Mac Extended Keyboard - it cannot be this complicated?

I was renaming some files this evening and thought I'd use my number pad on my Mac Extended Keyboard. It's been two months and I am just discovering that the numbers are not working. No big deal, search out the good ole' Num Lock key. Well, there isn't one. I've come to the conclusion that the keys should just work but of course they do not. I did discover an interesting "feature" and that is when I press the Zero key on my extended keyboard it locks up any and all windows I have open and renders the computer useless. Pressing the 5 key on the number pad unfreezes everything.

So why did I get the extended keypad again? Is there a secret combination of keys to get the numbers to work?