This may be a little tricky to recreate but here it is:

q = u'абвгде'
q.isalpha()
True

foo = u'ч'
foo.isalpha()
False

So the Russian character u'ч' and u'ё' as well as a bunch of others is
not recognized by isalpha as a alphabetic character, which it is a
matter of fact.
This applies to both capital and regular versions of the letters.

http://en.wikipedia.org/wiki/%D0%81
http://en.wikipedia.org/wiki/Che_(Cyrillic)

Using: Python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit
(Intel)] on win32