It's been awhile since I rebuilt Python and ran the test suite. This evening I noticed this on my Mac (OS X 10.5): test_thread Unhandled exception in thread started by > Traceback (most recent call last): File "/Users/skip/src/python/trunk/Lib/test/test_thread.py", line 51, in task self.done_mutex.release() thread.error: release unlocked lock Unhandled exception in thread started by > Traceback (most recent call last): File "/Users/skip/src/python/trunk/Lib/test/test_thread.py", line 51, in task self.done_mutex.release() thread.error: release unlocked lock Unhandled exception in thread started by > Traceback (most recent call last): File "/Users/skip/src/python/trunk/Lib/test/test_thread.py", line 51, in task self.done_mutex.release() thread.error: release unlocked lock Unhandled exception in thread started by > Traceback (most recent call last): File "/Users/skip/src/python/trunk/Lib/test/test_thread.py", line 51, in task self.done_mutex.release() thread.error: release unlocked lock Oddly enough, this didn't cause the test to fail. Is this a known problem? Should I open a ticket? Skip