Yes I'm using svn credentials via the Credentials plugin. I've also populated all my slaves with an "svn.simple" auth cache entry (to work around numerous past svn auth failures.) This was working fine until very recently. Here's output from my sanity check job on the AIX 5.3 slave. I find the "com.ibm.jsse2" suspicious, don't recall ever seeing that in a stack trace.

16:54:23 Building remotely on aix.aix5333 (pkg_aix64 pkg_aix53_64 run_pkg_aix53_32 run_pkg_aix64 run_pkg_aix32 pkg_aix53_32 pkg_aix32) in workspace /home/jenkins/workspace/bootstrap/bits/32/label/pkg_aix53_32/os/aix
16:54:23 Updating https://svn.voltage.com/svn/buildconfig/trunk/ci at revision '2015-04-24T17:54:12.963 -0600'
16:54:23 ERROR: Failed to update https://svn.voltage.com/svn/buildconfig/trunk/ci
16:54:23 org.tmatesoft.svn.core.SVNException: svn: E175002: java.lang.NullPointerException
16:54:23 svn: E175002: OPTIONS request failed on '/svn/buildconfig/trunk/ci'
16:54:23 at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:106)
16:54:23 at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:90)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:764)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:371)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:359)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.performHttpRequest(DAVConnection.java:710)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.exchangeCapabilities(DAVConnection.java:627)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.open(DAVConnection.java:102)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVRepository.openConnection(DAVRepository.java:1032)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVRepository.getRepositoryUUID(DAVRepository.java:143)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNBasicDelegate.createRepository(SVNBasicDelegate.java:339)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNBasicDelegate.createRepository(SVNBasicDelegate.java:328)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.update(SVNUpdateClient16.java:482)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.doUpdate(SVNUpdateClient16.java:364)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.doUpdate(SVNUpdateClient16.java:274)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.old.SvnOldUpdate.run(SvnOldUpdate.java:27)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.old.SvnOldUpdate.run(SvnOldUpdate.java:11)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.SvnOperationRunner.run(SvnOperationRunner.java:21)
16:54:23 at org.tmatesoft.svn.core.wc2.SvnOperationFactory.run(SvnOperationFactory.java:1259)
16:54:23 at org.tmatesoft.svn.core.wc2.SvnOperation.run(SvnOperation.java:294)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:311)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:291)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:387)
16:54:23 at hudson.scm.subversion.UpdateUpdater$TaskImpl.perform(UpdateUpdater.java:157)
16:54:23 at hudson.scm.subversion.WorkspaceUpdater$UpdateTask.delegateTo(WorkspaceUpdater.java:162)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.perform(SubversionSCM.java:991)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:972)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:948)
16:54:23 at hudson.FilePath$FileCallableWrapper.call(FilePath.java:2688)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:121)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:49)
16:54:23 at hudson.remoting.Request$2.run(Request.java:325)
16:54:23 at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:68)
16:54:23 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
16:54:23 at java.util.concurrent.FutureTask.run(FutureTask.java:149)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
16:54:23 at hudson.remoting.Engine$1$1.run(Engine.java:69)
16:54:23 at java.lang.Thread.run(Thread.java:736)
16:54:23 Caused by: javax.net.ssl.SSLException: java.lang.NullPointerException
16:54:23 at com.ibm.jsse2.n.a(n.java:42)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:96)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:340)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:555)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:584)
16:54:23 at com.ibm.jsse2.j.write(j.java:9)
16:54:23 at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:76)
16:54:23 at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:134)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.sendData(HTTPConnection.java:321)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPRequest.dispatch(HTTPRequest.java:170)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:463)
16:54:23 ... 36 more
16:54:23 Caused by: java.lang.NullPointerException
16:54:23 at com.ibm.jsse2.r.a(r.java:76)
16:54:23 at com.ibm.jsse2.bb$d_.a(bb$d_.java:14)
16:54:23 at com.ibm.jsse2.hb.q(hb.java:256)
16:54:23 at com.ibm.jsse2.gb.p(gb.java:87)
16:54:23 at com.ibm.jsse2.tc.h(tc.java:215)
16:54:23 at com.ibm.jsse2.tc.g(tc.java:419)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:461)
16:54:23 at com.ibm.jsse2.j.write(j.java:23)
16:54:23 ... 41 more
16:54:23 ERROR: Subversion update failed
16:54:23 java.io.IOException: remote file operation failed: /home/jenkins/workspace/bootstrap/bits/32/label/pkg_aix53_32/os/aix at hudson.remoting.Channel@370650bc:aix.aix5333: java.io.IOException
16:54:23 at hudson.FilePath.act(FilePath.java:985)
16:54:23 at hudson.FilePath.act(FilePath.java:967)
16:54:23 at hudson.scm.SubversionSCM.checkout(SubversionSCM.java:897)
16:54:23 at hudson.scm.SubversionSCM.checkout(SubversionSCM.java:833)
16:54:23 at hudson.scm.SCM.checkout(SCM.java:484)
16:54:23 at hudson.model.AbstractProject.checkout(AbstractProject.java:1270)
16:54:23 at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:609)
16:54:23 at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
16:54:23 at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:531)
16:54:23 at hudson.model.Run.execute(Run.java:1741)
16:54:23 at hudson.matrix.MatrixRun.run(MatrixRun.java:146)
16:54:23 at hudson.model.ResourceController.execute(ResourceController.java:98)
16:54:23 at hudson.model.Executor.run(Executor.java:374)
16:54:23 Caused by: java.io.IOException
16:54:23 at hudson.scm.subversion.UpdateUpdater$TaskImpl.perform(UpdateUpdater.java:211)
16:54:23 at hudson.scm.subversion.WorkspaceUpdater$UpdateTask.delegateTo(WorkspaceUpdater.java:162)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.perform(SubversionSCM.java:991)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:972)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:948)
16:54:23 at hudson.FilePath$FileCallableWrapper.call(FilePath.java:2688)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:121)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:49)
16:54:23 at hudson.remoting.Request$2.run(Request.java:325)
16:54:23 at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:68)
16:54:23 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
16:54:23 at java.util.concurrent.FutureTask.run(FutureTask.java:149)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
16:54:23 at hudson.remoting.Engine$1$1.run(Engine.java:69)
16:54:23 at java.lang.Thread.run(Thread.java:736)
16:54:23 at ......remote call to aix.aix5333(Native Method)
16:54:23 at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1360)
16:54:23 at hudson.remoting.UserResponse.retrieve(UserRequest.java:221)
16:54:23 at hudson.remoting.Channel.call(Channel.java:753)
16:54:23 at hudson.FilePath.act(FilePath.java:978)
16:54:23 ... 12 more
16:54:23 Caused by: hudson.scm.subversion.UpdaterException: failed to perform svn update
16:54:23 at hudson.scm.subversion.UpdateUpdater$TaskImpl.perform(UpdateUpdater.java:211)
16:54:23 at hudson.scm.subversion.WorkspaceUpdater$UpdateTask.delegateTo(WorkspaceUpdater.java:162)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.perform(SubversionSCM.java:991)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:972)
16:54:23 at hudson.scm.SubversionSCM$CheckOutTask.invoke(SubversionSCM.java:948)
16:54:23 at hudson.FilePath$FileCallableWrapper.call(FilePath.java:2688)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:121)
16:54:23 at hudson.remoting.UserRequest.perform(UserRequest.java:49)
16:54:23 at hudson.remoting.Request$2.run(Request.java:325)
16:54:23 at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:68)
16:54:23 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:314)
16:54:23 at java.util.concurrent.FutureTask.run(FutureTask.java:149)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
16:54:23 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
16:54:23 at hudson.remoting.Engine$1$1.run(Engine.java:69)
16:54:23 at java.lang.Thread.run(Thread.java:736)
16:54:23 Caused by: org.tmatesoft.svn.core.SVNException: svn: E175002: java.lang.NullPointerException
16:54:23 svn: E175002: OPTIONS request failed on '/svn/buildconfig/trunk/ci'
16:54:23 at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:106)
16:54:23 at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:90)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:764)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:371)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:359)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.performHttpRequest(DAVConnection.java:710)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.exchangeCapabilities(DAVConnection.java:627)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.open(DAVConnection.java:102)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVRepository.openConnection(DAVRepository.java:1032)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.DAVRepository.getRepositoryUUID(DAVRepository.java:143)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNBasicDelegate.createRepository(SVNBasicDelegate.java:339)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNBasicDelegate.createRepository(SVNBasicDelegate.java:328)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.update(SVNUpdateClient16.java:482)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.doUpdate(SVNUpdateClient16.java:364)
16:54:23 at org.tmatesoft.svn.core.internal.wc16.SVNUpdateClient16.doUpdate(SVNUpdateClient16.java:274)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.old.SvnOldUpdate.run(SvnOldUpdate.java:27)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.old.SvnOldUpdate.run(SvnOldUpdate.java:11)
16:54:23 at org.tmatesoft.svn.core.internal.wc2.SvnOperationRunner.run(SvnOperationRunner.java:21)
16:54:23 at org.tmatesoft.svn.core.wc2.SvnOperationFactory.run(SvnOperationFactory.java:1259)
16:54:23 at org.tmatesoft.svn.core.wc2.SvnOperation.run(SvnOperation.java:294)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:311)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:291)
16:54:23 at org.tmatesoft.svn.core.wc.SVNUpdateClient.doUpdate(SVNUpdateClient.java:387)
16:54:23 at hudson.scm.subversion.UpdateUpdater$TaskImpl.perform(UpdateUpdater.java:157)
16:54:23 ... 15 more
16:54:23 Caused by: javax.net.ssl.SSLException: java.lang.NullPointerException
16:54:23 at com.ibm.jsse2.n.a(n.java:42)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:96)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:340)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:555)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:584)
16:54:23 at com.ibm.jsse2.j.write(j.java:9)
16:54:23 at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:76)
16:54:23 at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:134)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.sendData(HTTPConnection.java:321)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPRequest.dispatch(HTTPRequest.java:170)
16:54:23 at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:463)
16:54:23 ... 36 more
16:54:23 Caused by: java.lang.NullPointerException
16:54:23 at com.ibm.jsse2.r.a(r.java:76)
16:54:23 at com.ibm.jsse2.bb$d_.a(bb$d_.java:14)
16:54:23 at com.ibm.jsse2.hb.q(hb.java:256)
16:54:23 at com.ibm.jsse2.gb.p(gb.java:87)
16:54:23 at com.ibm.jsse2.tc.h(tc.java:215)
16:54:23 at com.ibm.jsse2.tc.g(tc.java:419)
16:54:23 at com.ibm.jsse2.tc.a(tc.java:461)
16:54:23 at com.ibm.jsse2.j.write(j.java:23)
16:54:23 ... 41 more