I have 2 users on this machine. When I play a movie on mine I get a gray screen but I can hear the sound. But when I go into the other user it works fine. I reinstalled the divx 4 codec but it didn't help. I'm sick of having to go into my girlfriends account and to watch a movie.
This isn't a fix... I don't even know if it will be an effective work-around. Navigate to the folder 'Program Files\Windows Media Player' and launch mplayer2.exe. It's the old classic version of Media Player... I don't know if it will pick up on the divx codec or not.