Something that comes to mind: the stack traces in both issues show similar crashes where Tk is calling into OS X AppKit to create or modify a window.  Since a left paren is being typed, it seems to me the most likely scenario is that the left paren is completing a recognized token and IDLE is attempting to display a calltip (Lib/idlelib/CallTipWindow.py). That shouldn't be a problem, of course.  Also, note the exception class: NSInternalInconsistencyException.  That sounds suspicious.  I've found a few other reports, all from 10.8, of other non-Tk, non-Python apps with similar crashes.  I'm still not able to reproduce it myself.  Both reports here were with 10.8.2 and with ActiveTcl 8.5.11 or .12.  Can anyone reproduce the crash with the current 10.8.3 and ActiveTcl 8.5.13, which does contain some significant fixes for OS X?  And also, if so, verify that it is a calltip causing the problem?  To check that, in either an IDLE shell or edit window, typing ( at the beginning of a line should not cause a calltip to be created so, if there is a connection, there should not be a crash.  But then typing something like "open(" should cause a calltip to be created.  A crash of this sort is almost certainly a problem in either OS X or in Tk and not Python.  In any case, if we can't find a way to reproduce the problem reliably, there isn't much we can do about it.