Is this on a laptop? Check to see if you have it set to a function mode, each button on the number pad usually has a secondary function, but if you have numlock on it will normally treat them as numbers.
Oh, so you are having issues with the numbers that are immediately above the letters on the keyboard. Do the number keys have little pictures on them beside the numbers that arent the standard symbols that go with them?
Near your ctrl and alt keys on one side you should see a button labeled FN, its your function key, try hitting that a few times to make sure its not stuck, then see if your numbers work again, if they dont, try holding it and hitting a number and see if it behaves right.