wxAssert error on closing app, after all threads are stopped

Hello,
I’m having a bit of trouble debugging and app that kicks off up to independent wx.lib.delayedresult threads. The main app receives the wxCloseEvent and aborts using the AbortEvent() exception check. The closeevent function waits until .isAlive() returns False for each thread. Every now and then I get an error from wxWidgets stating “wxrefcounter:decref() invalid ref data count”. I assume this means one the threads is not properly shutdown as the reference count is out of whack. Can someone tell me how to determine which thread is causing the issue or how to solve this problem?

Thanks

Andrew