Mass Effect crash at C-Sec on Steam

I've recenlty reinstalled ME1 from Steam and I'm trying to replay it, but I'm getting a weird error messsage when I get to the C-Sec academy. I've pretty much just started the game, I'm going to get Wrex from C-Sec, and the game crashes while I'm in the elevator and Kaidan is talking about Edan Prime. The error message is:

First 4 bytes read is zero from ..\BioGame\CookedPC\Maps\STA\PLC\BIOA_STA30_06_PLC.SFM

Anyone seen this before? I've seen a few other "First 4 bytes..." messages in other forums, but I haven't seen a single answer about it. Some say it's the video card drivers, some say other things. I dunno.