It's widely reported. You'll have to complain to the CODEC author.
In the meantime, try latest video and audio drivers.
There will be no fix from Microsoft on this one.
When i play/single click some video files (Xvid) explorer crashes, while its trying to build the thumbnail. These files are not in the my documents folder and can be played through one program that i have (VideoLAN)but most programs ie win media player cant play it.