Comment 8 for bug 235011

OK.
I think I've a theory about that...
1. did you upgrade your gutsy to become a hardy???
2. did you had your w32codecs, mplayer from the era of gutsy???
will if the above is true I have faced the same problem you need to updated the medibuntu repositories in you software sources to become a hardy ones
if they don't yell to update these two packages then you will need to do it manually

# sudo apt-get autoremove w32codecs mplayer
# sudo apt-get install w32codecs mplayer

I don't know the cause of that but that what happened with me :-/

for medibuntu try:
https://help.ubuntu.com/community/Medibuntu

don't forget to remove the old one.
please keep me updated.