I've experienced strange error in my [future?] plugin, which utilizes tool installation. After upgrading to custom core, tool installation fails with a IncompatibleClassChange exception.

Probably, change has been caused by https://github.com/jenkinsci/jenkins/commit/b1267334b97c011f682e6d9b9130757bd8ca1c55

Oct 06, 2013 3:00:48 PM hudson.util.ProcessTree$OSProcess killByKiller
WARNING: Failed to kill pid=6540
java.io.IOException: Remote call on channel failed
at hudson.remoting.Channel.call(Channel.java:723)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.CygwinProcessKiller.kill(CygwinProcessKiller.java:60)
at hudson.util.ProcessTree$OSProcess.killByKiller(ProcessTree.java:221)
at hudson.util.ProcessTree$Windows$1.kill(ProcessTree.java:418)
at hudson.util.ProcessTree$Windows$1.killRecursively(ProcessTree.java:412)
at hudson.util.ProcessTree.killAll(ProcessTree.java:147)
at hudson.Proc$LocalProc.destroy(Proc.java:379)
....
at hudson.remoting.Engine$1$1.run(Engine.java:63)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IncompatibleClassChangeError: vtable stub
at java.util.ArrayList.<init>(ArrayList.java:164)
at hudson.util.CopyOnWriteList.replaceBy(CopyOnWriteList.java:127)
at hudson.util.PersistedList.replaceBy(PersistedList.java:78)
at hudson.tools.ToolInstallation.<init>(ToolInstallation.java:102)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.CygwinKillerInstallation.<init>(CygwinKillerInstallation.java:44)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.CygwinKillerInstallation.forNode(CygwinKillerInstallation.java:49)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.util.CygwinKillHelper.getCygwinHome(CygwinKillHelper.java:180)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.util.CygwinKillHelper.getSubstitutedHome(CygwinKillHelper.java:163)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.util.CygwinKillHelper.getCygwinBinaryCommand(CygwinKillHelper.java:129)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.util.CygwinKillHelper.execCommand(CygwinKillHelper.java:108)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.util.CygwinKillHelper.isCygwin(CygwinKillHelper.java:78)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.CygwinProcessKiller$KillerRemoteCall.call(CygwinProcessKiller.java:112)
at com.synopsys.arc.jenkinsci.plugins.cygwinprocesskiller.CygwinProcessKiller$KillerRemoteCall.call(CygwinProcessKiller.java:87)
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$1.call(InterceptingExecutorService.java:72)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)