Comment 22 for bug 415101

This appears to be the commit that fixes this for emacs23. It is not a terribly complex fix so patching Ubuntu's 22 may not be too hard.

http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=3715ffe3e3b2c64d113bf26d94aab559f8559e83

The quick workaround mentioned in the above linked bug reports is to start emacs with GDK_NATIVE_WINDOWS=1 which I can confirm fixes the dynamic menu problems, at least for python-mode.