This is clearly a Tkinter rather than Mac issue, so I am unassigning this from Ronald.  This appears to be the same problem as the one Mark described in msg102301.

>>> import locale
>>> locale.nl_langinfo(locale.CODESET)
'US-ASCII'
>>> import _tkinter
>>> locale.nl_langinfo(locale.CODESET)
'UTF-8'

This happens in both 2.6 and 2.7, but seems to be deliberate.  As Mark wrote in msg102328:

"""
There's still the issue of the Tkinter import changing the locale, but that seems to be out of Python's control.  As far as I can tell, it happens when the module initialization calls Tcl_FindExecutable, which is part of the Tcl library itself.  This may well be deliberate:  see

http://www.tcl.tk/cgi-bin/tct/tip/66.html
"""

What is still unclear to me, is why after CODESET changes to 'UTF-8', 2.6 thinks that '\xff' is a letter, but 2.7 does not.

Of course, '\xff' makes little sense in 'UTF-8', but why does the answer change between versions?