Thought I'd point the original poster to
this thread that deals with exactly the problem he's having. There's some kind of recurring problem that causes faces.dat to become corrupted. After a year or two of simming the game will crash at the point where it tries to save faces.dat. Renaming/deleting the file is only a temporary fix; the newly generated faces.dat will itself become corrupted shortly.
Andreas is looking over my league files to see if he can determine the source of the problem. Until something is discovered, the best "fix" (other than disabling FaceGen) is to make constant backups of faces.dat and copy the backup over the corrupted version whenever the game crashes on your during a save. It's hideously inconvenient and you'll still lose some of your picture associations... hopefully there'll be a permanent fix coming soon.