Thanks Raze - yes, all those files are in the save folder, which is about 15MB; I'd only been playing for about an hour when I made the save. The file names haven't changed and are consistent, but the folder/files (and in fact every folder/file on my C: drive) are marked as "Read-only." But I'm not sure whether or not they were marked as such before the problem as well, and whenever I try to "unset read-only" attribute for the save folders/files (or any other folders/files), the attribute is simply re-applied when I re-check the folder properties afterwards.
(This also didn't work:
http://support.microsoft.com/kb/256614)
