Click start -> run
Type dxdiag and press enter. Click no.
Click on the input tab and look to see if it lists any problems with your devices. If so, please post what it says here.
Remove your keyboard from the device manager entirely, then disconnect it from the computer.
Restart without the keyboard attached (if you can, some POST systems won't allow that) and then shut down the PC, re-attach the keyboard, and power it back up.
Reinstall the drivers and what-have-you, and see if the problem still persists.
