I've encountered the same "silent exit" problem in a multi-threaded Python Tkinter program also. I'm guessing that the Python interpreter hits an error starting a thread, so it calls exit(), and that the thread changes in cygwin 1.5.19 relative to 1.5.18 caused the problem we're seeing. My program worked again after reverting the "cygwin" package back to 1.5.18. I can be reached at http://www.jimbrooks.org __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/