[Matplotlib-users] 'module' object has no attribute 'instancemethod'

[klo uo <kl...@gm...>]

Out of the blue, I started getting this messages while plotting with MPL
1.2.1:

========================================
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\matplotlib\backends\backend_qt4.py",
line 244, in mouseMoveEvent
    FigureCanvasBase.motion_notify_event( self, x, y )
  File "C:\Python27\lib\site-packages\matplotlib\backend_bases.py", line
1724, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\Python27\lib\site-packages\matplotlib\cbook.py", line 343, in
process
    proxy(*args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\cbook.py", line 215, in
__call__
    mtd = new.instancemethod(self.func, self.inst(), self.klass)
AttributeError: 'module' object has no attribute 'instancemethod'
========================================

I didn't install any new package or change my Python installation in any
way, which makes this hard for me to solve. The message appears when I move
my mouse pointer inside plot window. I first removed matplotlibrc from my
"home" folder, and it happens again regardless backend changed this way
from wx to tk (which is default). I set backend to qt4 also, but it's just
the same.

Any ideas?