.mkv playback freezes

I have a few large (8-9gb) .mkv files that freeze at a certain point during playback. No matter what player I use (tried MPC and VLC) the freeze occurs at the exact same time (for example, one movie freezes at the 00:55:48 mark). If I try to fast forward to a point beyond that, the video will never start to play. I thought it might originally be a problem with the file, but no one else with this file has the problem, and the problem is occurring on 4 different movies (they all freeze at different points between about 16 minutes in, to an hour in).

It shouldn’t be a hardware problem, I’m on a Q9550 quad core processor, have 8GB RAM, and a GeForce 9800GTX+ video card. I’m on Vista Premium 64-bit.

Yes, I’m pretty good with computers and video and can’t quite figure out what’s going on. The only thing I could think of was a bad file, but ruled this out because the number of files with similar symptoms, plus the fact that other people are having success with the file.

Anyone have any ideas?