You are not alone! This problem was introduced by Nvidia drivers after 163.75. If you go back to those it works fine. It is not codec or file related. It happens with AVI's. I have x64 so I am uncertain if this affects 32 bit or not. The Mediacentre in x64 uses a 64 bit player, this may be related in some way. I do find AVI's play fine in 64 bit media player though.