See this:
http://forum.bsplayer.org/viewtopic.php?t=3562
This has to do with the AVI-splitter. Re-install DirectX and beware when installing ViPlay or other media players that comes with their own splitter (see link in the last post in the thread) Be careful if you install the splitter that comes with it!
The reason that VLC works is that it comes with its own codecs, it doesn't use the ones you've installed separately.