I did a lot of reading and became convinced that my problems were caused by mouse clicking with my right hand. Sure enough, the orthopedist said I had an early case of carpal tunnel syndrome. He gave me a splint to wear at night and while computing, and told me to take Aleve to reduce inflammation. The splint holds one's wrist perfectly straight. Most people curve their wrists up at night while sleeping, and the splint keeps that joint straight so that one's bones can't squish the carpal tunnel nerve. The Aleve keeps the swelling of nearby muscles and tendons down, so that the nerve can relax.
I also got a split-style keyboard and marble mouse at work. These help keep my wrist in the straight position while computing. The mouse distributes mousework over a lot more muscles than a traditional mouse. The keyboard was pretty easy to get used to; the mouse was much harder. But I've got it now!
I did this for 3 weeks and everything felt much better. Now I just wear the splint at night (and I got one for my left hand, too, which was affected less severely but still a bit affected). I also try to take more frequent breaks from computing and knitting.
With all that as background, here are some easy ways to prevent holiday knitting injuries, posted by a knitter and massage therapist who is a member of the Common Cod Fiber Guild in Boston. Kristina is a member. Boy, I would be, too, if I lived there! Check out their events lineup - they have already hosted Stephanie Pearl-McPhee, Franklin Habit, and Susan Gibbs, and Clara Parkes is next. Green with envy down here in PA...