Can people NOT BE SO FUCKING RETARDED? VLC is a terrible player, it is not designed for playback, and it fails to do pretty much any playback you can throw at it. It is designed for streaming and that is all it should ever be used for.
If you have ANY codec packs, remove them. Remove any extra players and anything else too. Then install the latest CCCP and run your shit in MPC-HC. Alternatively, mplayer-uau, kovensky just did a new build which you can find on google. More likely your config is just broken though, and you can play around until it works. But I would suggest letting the CCCP configuration app reset everything. My above post will find your problem, but this will probably fix the basics. Also FFMS2 in avisynth will load them for editing anyway, as it uses it's own decoders and splitters. Either way, ignore post-it and HalOfBorg, neither of them have any idea what they're talking about and are only offering the same misguided help they always do.