My mother had trigger finger. Its kinda like Carpel Tunnel Syndrome. Its from repetative motion. She got it from using a computer mouse at work all day long for years and years. Basically it keeps you from being able to straighten your finger out properly. She had surgery and it was repaired.
I think I also read that Andy Aledort (Guitar World) had this and had to have an operation. Its a real problem but it can be fixed. Unfortunately I think it will put your guitar playing on hold for about a year. :( I have been doing lots of stretching and warming up after reading about this kind of stuff. Sean Conklin one of the GT instructors has a story about how he had to give up guitar for a year because of a similar situation and his story is what made me take proper stretching and warm ups seriously. Hope this helps and good luck. Let us know how it goes.