Vista key combination to disable keyboard

Hi folks,
Earlier I was called out to try and fix a keyboard. It seems someone pressed a key combination that for all intensive purposes disabled the keyboard. Caps lock didnt light up and neither did num or shift lock. The mouse stayed working and the curious thing is so did a selection of keys like the windows key and the right click key on the keyboard. A simple reboot fixed the problem but I'm just looking for the combination that caused it. There is no third party keyboard software on the computer the only thing I can think of that might have been a contributing factor was that the person was using a usb keyboard on a laptop(the key combo in question caused the 2 keyboards to stop working). If anyone can help me shed some light on this it would be greatly appericiated.