[Blucar1]

So the other day, after a friend gets out of my car and I drive off, I noticed my passenger door would not lock. First though: 'Eh, just didn't drive fast enough for the locks to engage', so naturally I sped up. Nothing. Hit the central lock button, nothing. Finally, I reach over to push it down manual and it wouldn't move. I parked the car thinking it just needed to reset or something and its still not locking at all.

Now I'm ALL for a DIY fix. Any ideas as to what it is before I take it to the stealership?