My Mom has just called me in a panic, she was typing and suddenly none of the keys will work - it seems as if she hit some key and accidentally locked the keyboard. The screen still works with the mouse, it is just the keyboard that appears to be locked. Does anyone know if there is a way your keyboard can become accidentally locked, and how to unlock it?

She's activated one of the Accessibility options -- most likely FilterKeys. There's probably an icon in the tray that she can close with the mouse. However, the easiest way to make sure everything is turned off is to go to the Control Panel and access Accessibility Options. Under the "Keyboard" tab, make sure StickyKeys, FilterKeys, and ToggleKeys are all unchecked (turned off).

You turn on FilterKeys by holding the right shift key down for 8 seconds. This is how she did it "accidentally".
You turn on StickyKeys by pushing the shift key five times.
You turn on ToggleKeys by holding the NUMLOCK down for 5 seconds.

Thanks, it sounds very promising - I always wondered where you changed those settings. I am sure that is what she did!