Hi,
I am running jenkins v.1487 through tomcat7.
I get the error

WARNING: Failed to monitor user at slave for Free Swap Space
java.io.InvalidClassException: hudson.node_monitors.SwapSpaceMonitor$MonitorTask; local class incompatible: stream classdesc serialVersionUID = 1, local class serialVersionUID = 1184166703664094906
at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:562)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.UserRequest.deserialize(UserRequest.java:182)
at hudson.remoting.UserRequest.perform(UserRequest.java:98)
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(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)

It seems that this is a bug. I am not familiar enough with jenkins to assess if it can cause great problems, or not.

BR,
David