Intermittent slave disconnections with secondary symptoms

Another intermittent problem.
Master is linux, target is freebsd 4.9.

FATAL: Unable to delete script file /var/tmp/hudson60616.sh
hudson.util.IOException2: remote file operation failed
at hudson.FilePath.act(FilePath.java:313)
at hudson.FilePath.delete(FilePath.java:510)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:70)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:34)
at hudson.model.Build$RunnerImpl.build(Build.java:130)
at hudson.model.Build$RunnerImpl.doRun(Build.java:105)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:231)
at hudson.model.Run.run(Run.java:756)
at hudson.model.Build.run(Build.java:85)
at hudson.model.ResourceController.execute(ResourceController.java:70)
at hudson.model.Executor.run(Executor.java:82)
Caused by: java.io.IOException: already closed
at hudson.remoting.Channel.send(Channel.java:316)
at hudson.remoting.Request.call(Request.java:81)
at hudson.remoting.Channel.call(Channel.java:390)
at hudson.FilePath.act(FilePath.java:310)
... 10 more
Build was aborted
FATAL: null
java.lang.NullPointerException
at hudson.tasks.ArtifactArchiver.perform(ArtifactArchiver.java:78)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:309)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:297)
at hudson.model.Build$RunnerImpl.post2(Build.java:118)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:282)
at hudson.model.Run.run(Run.java:774)
at hudson.model.Build.run(Build.java:85)
at hudson.model.ResourceController.execute(ResourceController.java:70)
at hudson.model.Executor.run(Executor.java:82)