The stupidest thing ever happened to me! I used to be able to play some 720p mkv's that i had downloaded, they played really nicelly with vlc, no complaints, but it's been 3 days and I can't seem to get my mbp (c2d 2.4ghz, 2Gb of RAM, nvidia 8600mgt 256MB) to play those old mkv files on vlc, or on a...