Toshiba Satellite L675D laptop keyboard is not working

My Toshiba Satellite L675D laptop keyboard is not working. The keys:
a, b, n, enter, 7 on number keyboard, and the left shift key, are not working at all.
I'm having to use either the on screen keyboard, or an external usb Logitech keyboard.
I have Windows 7 Home Premium, SP1.
Any advice is most welcome!
Thanks in advance!
- Jamie