Thanks, it was a problem with one of the replays, but now I'm getting another replay-related bug.
I moved them out of the folder to check which were bad and deleted them, but when I put all the good ones back in, the last one in the listing doesn't appear ingame (Which in my case is WallFlip, a default replay I think.)
This one isn't nearly as much of a problem, but I'd like to know if it's possible to fix it.