Have you tried using an ergonomic keyboard? My "mouse elbow" is all but gone now that I use one at work and home.

I've also heard that relearning to type on a DVORAK keyboard (or just typing on a QWERTY that thinks it's a DVORAK thanks to toggling in Window's Regional and Language Options) can help. I read online (so it must be true!) that Dvorak minimizes carpal tunnel since the most used keys are closer together.

I've been considering trying this too (after I finish my manuscript... don't need anything else to slow me down...)