IllegalThreadStateException in JVM Console

[jason]

Strange.
I'm running a threaded applet in IE using the 1.3.1 JRE.
While the applet is running I dump the thread list ('t') in the Java
Console and, if done several times in a row, it eventually throws the
following exception:

java.lang.IllegalThreadStateException
at java.lang.ThreadGroup.add(Unknown Source)
at java.lang.Thread.init(Unknown Source)
at java.lang.Thread.<init>(Unknown Source)
at com.jci.metasys.command.UpdateHeaderMcrCmd.execute
at com.jci.framework.command.CommandServiceLocal.processCommand
at com.jci.framework.command.AbstractCommand.processCommand
...

The exception is thrown when the applet attempts to create a new
thread and add it to the thread group.
This only happens when attempting to view the thread list via the
console. If left to run on it's own the exception never gets thrown.
Once it is thrown, it keeps getting thrown every time the applet
attempts to create the thread (it repeats every few seconds).

Maybe I'm missing something but I wouldn't expect an action in the
console to affect the executing code.

Any thoughts?
Thanks.
jason