I used to fix these things for a living... hardest part is taking it apart... you can follow this thread for that.
http://www.blackberryforums.com/gene...t-housing.html
Then just get a toothbrush and some alcohol and scrub the metal contacts on the board. Also scrub the small black carbon dots on the back of the keys. Then WAIT! make sure all the alcohol had dried before you put it back together and power it up. works everytime. :()