Couple of things to try:
1. While in safe mode, delete the drivers for the Keyboard. This will cause
windows to re-detect the keyboard the next time you reboot and will reload
the device drivers.
2. Try another keyboard. The driver within Windows could be corrupt and
installation a new keyboard will force Windows to load a new driver.
3. Check the keyboard manufacturers website (if it's a "non-standard"
keyboard) and see if there is an updated driver or if there is a know with
the driver you are currently using for your keyboard.
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