I can't reproduce this. Can you please post the entire traceback? It would be preferable if you could also show the exact code that's causing the problem, typed from a python command prompt (see my example below).

I can reproduce the error if I pass a list to ps.path.splitext(), which is what I suspect you're doing:

>>> os.path.splitext(['c:\\blah.ext'])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/posixpath.py", line 95, in splitext
    return genericpath._splitext(p, sep, altsep, extsep)
  File "/usr/lib/python2.6/genericpath.py", line 91, in _splitext
    sepIndex = p.rfind(sep)
AttributeError: 'list' object has no attribute 'rfind'

And you probably want: os.path.splitext("C:\\blah.ext"), so as to escape the backslash.