The problem here occurs when IDLE on OS X is launched without an initial shell window, either by setting the option in IDLE preferences or from the command line (/usr/local/bin/idle -e) *and* IDLE detects that the version of Tk in use is one of the suspect OS X versions and is attempting to warn the user with this message in the shell window:

 WARNING: The version of Tcl/Tk (8.5.9) in use may be unstable.
 Visit http://www.python.org/download/mac/tcltk/ for current information.

Unfortunately, that doesn't work if there is no shell window.

The workaround is to follow the instructions at the above link and, if possible, install an up-to-date Tcl/Tk 8.5 from ActiveState.  If that is not possible, then launch IDLE from the command line with an initial shell window:

/usr/local/bin/idle2.7 -i

and be sure to change the preference to always launch with a shell window.