Calling all guitarists...

...I need your advice.

When I was playing guitar I was never very good at it and now that I'm trying it again I'm still pretty crappy. However, my major stumbling block right now is pain. I'm developing some lovely callouses on the tips of my fingers (which is good) but my wrist is killing me. I can only play for a few minutes before I have to stop.

Any pointers for strengthing those wimpy wrist muscles?

-m