[Python-mode] void variable py-buffer?

[Daniel Flesner]

when i'm editing a python .py file in a buffer and pull down the
Edit/Paste menu i get the following error:

  Debugger entered--Lisp error: (void-variable py-buffer)
    (buffer-live-p py-buffer)

i'm running GNU Emacs 23.2.1, is this a bug or a configuration error on
my part somewhere?

thanks,
daniel