I need to preach here for a moment.
My wrist, hand, and forearm problems (aching finger joints, a mild annoyance; bouts of tendonitis, a major annoyance; feelings like sparklers going off in the ends of the fingers, occasional loss of fine control in the fingers, extremely sore wrists with restricted motion, inner forearms too tender to touch) used to force me to completely stop playing, and typing at regular intervals. I would typically have to lay off almost completely for at least one week in every five, and I didn't type (or practice) anything like as much at this point of my life anyway.
This seems to have been completely caused by poor typing habits. For those who don't know, you should make sure than your typing position leaves the wrist as close to straight as possible, and the forearms as close to horizontal as practical.
I now have a more supportive chair (so I don't slouch), set at a height where the bottom of my elbows are a little higher than the top of the keys, and I 'float' my hands; only the fingers touch the keyboard. The line from elbow along the forearm to the knuckle is almost completely straight and horizontal. I touch-type, so I also use a split-layout ergonimic keyboard (I like the MS Natural; some people prefer others), to avoid 'splaying' my hands so the my fingers are pointing straight ahead with the wrists angled in.
Since making these changes, I have almost no joint stiffness, absolutely no carpal tunnel-type problems, and the only time I've had any muscle soreness in this area is after a day where I spent four hours working on 'Tumeni Notes' (constant alternate 16th-note triplet arpeggios, with no chord held for longer than one beat).
http://www.jwz.org/gruntle/wrists.html
If you have any of these problems, you really really need to get it sorted out before you have _permanent_ damage. I was very very lucky; I have full function as long as I'm careful (not typing for long periods on non-ergonomic keyboards, using good posture). Some people never regain the normal use of their hands.
Also: mice, in and of themselves, are not evil. Going back and forth between mouse and keyboard is a good way to screw yourself up. If you have a task that needs both typing and mouse use, _learn the keyboard shortcuts_.
*breathe*
Seriously, folks. A new keyboard (and possibly chair) and a week or two of thinking hard about your posture until it becomes automatic, and you can avoid crippling yourself.
Here endeth the lecture.
- rfb