Just before Christmas, I developed really bad pains in my left wrist. After a few days I self-diagnosed these as being some kind of Repetitive Strain Injury from typing too much and more importantly, in a poor position. It got so bad that it was agony to type and I had to take a few days off.
After reading around the subject, I got myself a Microsoft Natural Ergonomic Keyboard 4000 and I have to say things got better immediately. Now, I get the odd twinge, but it’s only when I revert to poor wrist position, which is actually quite hard with this keyboard. You should have your wrists perfectly straight, not bent on the horizontal plane, at all.
If you do a lot of typing (and most of us do more and more) I strongly urge you to get one of these, or at least a similar model from someone else. RSI will probably strike you at some point and prevention is better than cure.
I hope you know me well enough for this to be superfluous, but I’m not getting a backhander from Redmond for writing this and I paid retail for the keyboard. But, it’s easy to focus on what the Big Fella is doing wrong sometimes and forget that they do an awful lot right.
Well, apart from their mobile strategy, obviously 
Spot on! I had exactly the same problem with my wrists last fall, and the cure was exactly same.
Thank god (and Bill G) for the keyboard! It saved my life.
The pic in my blog post shows my new keyboard:
http://www.blogs.s60.com/tommi/2005/12/sharing_your_pics_with_shozu.html
ps. I think I got my injury from having too many windows open simultaneously, and switching constantly between the windows with Alt-Tab. Did you left wrist hurt also from the outer joint?
Tommi - yeah, exactly the same place. But, while I do like lots and lots of windows, I very rarely use Alt-Tab for some reason. But the problem is the same.
So, people, let’s type careful out there.
Cheers
Russell