I have just checked:

This exception may be connected to this bug:

May 6, 2013 1:56:30 PM org.apache.jk.common.ChannelSocket processConnection
WARNING: processCallbacks status 2
May 6, 2013 1:56:30 PM org.kohsuke.stapler.compression.CompressionFilter reportException
WARNING: Untrapped servlet exception
ClientAbortException: java.net.SocketException: Broken pipe
at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:369)
at org.apache.tomcat.util.buf.ByteChunk.flushBuffer(ByteChunk.java:448)
at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:318)
at org.apache.catalina.connector.OutputBuffer.close(OutputBuffer.java:274)
at org.apache.catalina.connector.CoyoteOutputStream.close(CoyoteOutputStream.java:104)
at java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:149)
at org.kohsuke.stapler.compression.FilterServletOutputStream.close(FilterServletOutputStream.java:36)
at java.io.FilterOutputStream.close(FilterOutputStream.java:143)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:301)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:130)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:216)
at java.io.BufferedWriter.close(BufferedWriter.java:248)
at org.dom4j.io.XMLWriter.close(XMLWriter.java:286)
at org.kohsuke.stapler.jelly.HTMLWriterOutput.close(HTMLWriterOutput.java:70)
at org.kohsuke.stapler.jelly.DefaultScriptInvoker.invokeScript(DefaultScriptInvoker.java:56)
at org.kohsuke.stapler.jelly.JellyClassTearOff.serveIndexJelly(JellyClassTearOff.java:112)
at org.kohsuke.stapler.jelly.JellyFacet.handleIndexRequest(JellyFacet.java:127)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:666)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
at org.kohsuke.stapler.MetaClass$12.dispatch(MetaClass.java:384)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:677)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:203)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:677)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:583)
at org.kohsuke.stapler.Stapler.service(Stapler.java:214)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:48)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:124)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:174)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:64)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:50)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:470)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:776)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:705)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:898)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at org.apache.jk.common.ChannelSocket.send(ChannelSocket.java:539)
at org.apache.jk.common.JkInputStream.doWrite(JkInputStream.java:162)
at org.apache.coyote.Response.doWrite(Response.java:560)
at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:364)
... 79 more
May 6, 2013 1:56:30 PM org.apache.jk.common.ChannelSocket processConnection
WARNING: processCallbacks status 2
May 6, 2013 1:59:28 PM hudson.slaves.SlaveComputer tryReconnect
INFO: Attempting to reconnect slave_node

I have been skimming the entire log at startup.

My log is totally overcrowded with the error:
hudson.plugins.collabnet.auth.CNProjectACL hasPermission
SEVERE: Improper Authentication type used with CNAuthorizationStrategy! CNAuthorization strategy cannot be used without CNAuthentication. Please re-configure your Jenkins instance.

I have tried to resolve it without luck yet.
It occurred after upgrading to 1.515 and updating all plugins to most recent state.
There was also an update for the Collabnet plugin.
It MAY be connected somehow but I (or should I say my guts) doubt it

The parts of interest/related are these:

INFO: Started all plugins
23.05.2013 13:34:27 jenkins.InitReactorRunner$1 onAttained
INFO: Augmented all extensions
.
.
.
INFO: Loaded all jobs
.
.
.

23.05.2013 13:34:46 hudson.plugins.collabnet.auth.CNProjectACL hasPermission
SEVERE: Improper Authentication type used with CNAuthorizationStrategy! CNAuthorization strategy cannot be used without CNAuthentication. Please re-configure your Jenkins instance.
.
.
.
23.05.2013 13:34:52 hudson.node_monitors.AbstractNodeMonitorDescriptor$Record run
WARNING: Node monitoring B00014_GUIDE_2 for Clock Difference aborted.
java.lang.InterruptedException
at java.lang.Object.wait(Native Method)
at hudson.remoting.Request.call(Request.java:146)
at hudson.remoting.Channel.call(Channel.java:672)
at hudson.model.Slave.getClockDifference(Slave.java:261)
at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:53)
at hudson.node_monitors.ClockMonitor$1.monitor(ClockMonitor.java:49)
at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:246)
23.05.2013 13:34:52 hudson.node_monitors.AbstractNodeMonitorDescriptor$Record run
WARNING: Node monitoring MIB1_GUIDE for Free Swap Space aborted.
java.lang.InterruptedException
at java.lang.Object.wait(Native Method)
at hudson.remoting.Request.call(Request.java:146)
at hudson.remoting.Channel.call(Channel.java:672)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:83)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:81)
at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:246)
23.05.2013 13:34:52 hudson.node_monitors.AbstractNodeMonitorDescriptor$Record <init>
WARNING: Previous Architecture monitoring activity still in progress. Interrupting
23.05.2013 13:34:52 hudson.node_monitors.AbstractNodeMonitorDescriptor$Record <init>
WARNING: Previous Free Disk Space monitoring activity still in progress. Interrupting
.
.
.
23.05.2013 13:34:52 hudson.node_monitors.AbstractNodeMonitorDescriptor$Record run
WARNING: Failed to monitor MIB1_GUIDE for Free Swap Space
java.io.IOException: Remote call on MIB1_GUIDE failed
at hudson.remoting.Channel.call(Channel.java:681)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:83)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:81)
at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:246)
Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.jvnet.hudson.Windows$MEMORYSTATUSEX
at org.jvnet.hudson.Windows.monitor(Windows.java:40)
at hudson.node_monitors.SwapSpaceMonitor$MonitorTask.call(SwapSpaceMonitor.java:109)
at hudson.node_monitors.SwapSpaceMonitor$MonitorTask.call(SwapSpaceMonitor.java:99)
at hudson.remoting.UserRequest.perform(UserRequest.java:118)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:326)
at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at hudson.remoting.Engine$1$1.run(Engine.java:58)
at java.lang.Thread.run(Unknown Source)
.
.
.
java.io.IOException: Remote call on MIB1_GUIDE failed
at hudson.remoting.Channel.call(Channel.java:681)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:83)
at hudson.node_monitors.SwapSpaceMonitor$1.monitor(SwapSpaceMonitor.java:81)
at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:246)
Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.jvnet.hudson.Windows$MEMORYSTATUSEX
at org.jvnet.hudson.Windows.monitor(Windows.java:40)
at hudson.node_monitors.SwapSpaceMonitor$MonitorTask.call(SwapSpaceMonitor.java:109)
at hudson.node_monitors.SwapSpaceMonitor$MonitorTask.call(SwapSpaceMonitor.java:99)
at hudson.remoting.UserRequest.perform(UserRequest.java:118)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:326)
at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at hudson.remoting.Engine$1$1.run(Engine.java:58)
at java.lang.Thread.run(Unknown Source)

And finally:
23.05.2013 13:44:44 hudson.remoting.SynchronousCommandTransport$ReaderThread run
SEVERE: I/O error in channel MIB1_GUIDE
java.io.IOException: Unexpected termination of the channel
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at hudson.remoting.Command.readFrom(Command.java:92)
at hudson.remoting.ClassicCommandTransport.read(ClassicCommandTransport.java:59)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:48)

oleg-nenashev suggests backporting amelioration: https://github.com/jenkinsci/jenkins/commit/bcdfb2860ffa4bef97ce01a20779b08472388231#commitcomment-4102101

Fix for https://issues.jenkins-ci.org/browse/JENKINS-19453 may resolve this issue.
BTW, symptoms are quite similar

I don't see the issue since JENKINS-19453.
Marking as resolved...