I pride myself on keeping a nice neat, and clean keyboard. As such I was shocked when the number pad on my external Logitech Wireless Internet suddenly stopped working! However it appears I shouldn’t have worried.

A quick google and look what I found: http://geekozoid.blogspot.com/2008/06/number-pad-numeric-keypad-not-working.html

Basically you need to:

Click on System->Preferences->Keyboard
Open Mouse Keystab.
Uncheck “Allow to control the pointer using the keyboard”

and then it works perfectly! Thanks GeekoZoid!