Since I made the upgrade to 12.04 I can't play WMA files. I added Medibuntu, install w64codecs, non-free-codecs but they don't work. I have also installed ubuntu-restricted-extras.
Ubuntu – How to play WMA files
codecswma
Related Solutions
I recommend smplayer and gecko-mediaplayer, which are the best mplayer frontend and browser plugin respectively. For codecs get ubuntu-restricted-extras. I also recommend the Comprehensive Multimedia & Video Howto tutorial.
smplayer 
gecko-mediaplayer
ubuntu-restricted-extras
I have the same problem with Xubuntu 14.04, too. Solution above didn't work for me. The only workaround I found was to play wmv files using mplayer from terminal (since skinned version fails to load).
Like mplayer [filename]
Hope it helps.
EDIT: found out, that XBMC can play wmv files as well.
Best Answer
I found the solution: remove the folder
.gstreamerin the home directory.