Installer register shutdown hook that performes cleanup (runs the cleaner in new process).
Due to change in JDK that was done in JDK6U2 this sometimes result in RejectedExecutionThread.
Exception while removing reference: java.util.concurrent.RejectedExecutionException:
java.util.concurrent.RejectedExecutionException
        at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.reject(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.execute(Unknown Source)
        at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
        at sun.awt.shell.Win32ShellFolder2$ComTask.execute(Unknown Source)
        at sun.awt.shell.Win32ShellFolder2$FolderDisposer.dispose(Unknown Source)
        at sun.java2d.Disposer.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
Exception while removing reference: java.util.concurrent.RejectedExecutionException
java.util.concurrent.RejectedExecutionException	
        at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.reject(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.execute(Unknown Source)
        at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
        at sun.awt.shell.Win32ShellFolder2$ComTask.execute(Unknown Source)
        at sun.awt.shell.Win32ShellFolder2$FolderDisposer.dispose(Unknown Source)
        at sun.java2d.Disposer.run(Unknown Source)


See also
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6612928

This doesn`t affect any installer functionality but leave unnecessary files in tempdir.
Probably it can also can leaving the uninstaller but I haven`t ever seen such an issue.