I am having similar problems. The thing that may be hanging you up is the fact that you usually have to set a bit in order to clear the interrupt flag, while in the ISR (more specifically: set the C0F/C1F bit, respectively...check out page 12-14 in the RM). Also, I had to setup the IMRL registers (I am trying to use the PIT, but not working correctly yet). The problem I have is that it will interrupt once, but then no more..check out my thread on PIT. but ya, start with what I have said, hopefully you will have more success then me!