Same thing happened to me:
http://www.peachparts.com/shopforum/showthread.php?t=233130
Turns out all I needed to do was blow compressed air/duster gas into the lock and then spray in graphite lubricant I got from Lowes key making area. Tons of old gunk sprayed out and the key worked better than ever, door worked fine after that. Of course, this just happened to me with my trunk too: I tried everything and it took so long it finally warmed up outside and my truck lock started working again. Could it be the oncoming cold?