Suddenly without me installing anything new, all of my .mkv files have stopped playing properly. With Zoom player and Media Player Classic, the video moves slower than usual while the audio moves at the proper SPEED and with VLC media player, the video freezes up completely. All other file FORMATS that I've tried playing since this happened continue to WORK perfectly fine with all three players. I have already tried REINSTALLING my Combined Community Codec Pack but it didn't make a difference.

I'm currently running Windows Vista on an HP Pavilion dv9700 notebook with:
3 GB RAM
AMD Turion 2 GHz Dual Core Processor
NVIDIA GeForce 7150M Graphics Card

Any ideas on solutions would appreciated.

Update:
Now Zoom player is coming up with the error message "Unable to play [[Eclipse] Fullmetal Alchemist Brotherhood - 05 (1280x720 h264) [3373DF87].mkv]
This may be due to a corrupt file, missing filters, filter conflicts, or hardware related issues." for all files, Media Player Classic just says it's opening the file while doing nothing until I close it, and VLC Player just plays audio while the video freaks out, GLITCHES, and freezes.