Try reinstalling the tablet driver, make sure it's the right one (for 32-bit or 64-bit). Also, it may help to flash or update your USB port drivers.
I've had times when I've had to reinstall the tablet driver several times before it worked. The tablet light still will come on anyways because it's being powered by the laptop regardless of whether it's working or not
I've got it to work for the moment, what's happening now it that if I stop moving the cursor for a few seconds, then sometimes the pen stops responding for a minute or so when I try to move it again. Oo It's frustrating.