Thanks for the report.  It appears that all that is needed to trigger the hang is any operation that invokes the IDLE EncodingMessage dialog ("Non-ASCII found, yet no encoding declared. Add a line like [...]") in IOBinding.py during a Save when IDLE is linked with the OS X Cocoa Tk 8.5 (or likely 8.6) as used with the python.org 64-bin/32-bit 10.6+ installers, for example, just opening a new edit window, inserting a non-ASCII character, and then trying to Save.  EncodingMessage subclasses the Tkinter SimpleDialog module and creates a new Toplevel root; I seem to recall other problems like this in the past.  The problem is not seen with the older Carbon Tk 8.4 or with an X11 Tk on OS X.