From the backtrace it shows you are linking with the Apple-supplied Tk (/System/Library/Frameworks/Tk.framework/Versions/8.5/Tk) framework. The Apple-supplied Tk 8.5 in OS X 10.6 was the first release of the Cocoa Aqua Tk. It has proven to be unusable with Python Tkinter and IDLE.  There have been numerous Python issues opened about it.  If you wish to use Tkinter on OS X 10.6, you should either supply and link with a different Tk 8.5, such as the ActiveState Tcl 8.5 or one you build yourself (either Cocoa, Carbon, or X11) or, if you don't need 64-bit support, link with the Apple-supplied Carbon Tk 8.4.  See http://www.python.org/download/mac/tcltk/ for current recommendations.

That said, it wouldn't explain crashes on Windows (can you produce a trace  for that?) and there's no guarantee you won't run into other bugs using a more recent Tk on OS X.  But you'll most likely be wasting your time if you try to debug anything with the Apple Tk 8.5 in 10.6.  Any Tk problems you find should be reported on one of the Tcl/Tk mailing lists, for example, the Mac-specific Tcl list (most easily accessed here: http://dir.gmane.org/gmane.comp.lang.tcl.mac) or the Tk bug tracker (http://tcl.sourceforge.net).

Unless there is evidence that Python is doing something wrong and you can provide a reproducible test case, this issue should be closed.