I've never understood the insistence on having passwords to get back to a certain level.
What exactly are you worried about? Someone hopping onto my game on my computer and screwing it up?
Anyway, game was going fine until I wanted to restart and closed the level only to find I was forced to start a new campaign because the game didn't feel like saving normally.
Really dampens the enjoyment, and I obviously didn't like it that much to start playing through it again.