I've had this exact same experience. On a somewhat related note, there may be 'pressure points' that occur in different sitting positions that may cause reduced blood-flow to the wrists, hands and fingers. I experience some RSI in my ring and pinky fingers for over a year and became very concerned that it would get worse. After partially alleviating the problems with a Kinesis Advantage keyboard, I actually discovered that the majority of the issues came from resting my elbows on my elbow rests throughout the day. This was putting pressure on the ulnar nerve and causing the issues in my ring and pinky fingers. It took me over a year to discover this, but when I did the symptoms rapidly went away. I also found that side-sleeping on my arm was doing a similar thing.

A friend of mine mentioned similar issues that resulted from pressure on the palms of the hands during long periods of typing (he's an editor for a magazine).

Hope that helps somebody out there.