dear fenzo have you tried entering in safe mode first
if its working even if it was for 5 seconds then it means that the board is fine and the fault is within the wire of the keyboard but if this keeps happening then try the following
1. Disconnect the device from the USB port.
2. Open device manager
3. Double-click the appropriate device category
4. Right-click your USB device, and then click Uninstall
5. Restart your computer.
6. Turn the power back on for the device, if necessary, and then plug the device into the USB port.
and if that doesnt solve the problem try installing the sp3 again if you are using XP