This has happened to me many times before. And the worst thing is, I can't predict it at all. I'll go for a year without magically re-setting my alarm in my sleep, and then all of a sudden I'll do it twice in a week. For a while, I had to put my alarm on the opposite side of my room, just so I'd have to physically get up to shut it off. It's good to know that others suffer from the same problems...