As an example:
...these "function keys" are often used in laptops that don't have a number pad like a full sized desktop keyboard will.
Often on the keyboard itself is a "function Key" often signified by a "Fn" on the key, pressing it will enable/disable the keypad ability. So if you're receiving that 4/5/6 when pressing a u/i/o, see if you have a key with "Fn" on it, if so try giving it a press and repeating the u/i/o.
Just wanted to say THANKS A BUNCH for posting this simple 'FIX'. I used to think I knew a thing or 2 about computers, but some of these functions I've just never discovered and thought the new wireless keyboard was to blame. I needed to simultaneously press Fn/Shift/NumLock on the laptop or just unlock the NumLock on the wireless keyboard. Now I know it was my own ignorance. Thanks again.