Not sure if this will help but I have the same problem when using an Apple Keyboard when connecting to a remote XP PC using Remote Desktop Connection. This problem was solved by pressing the key that's in the Num Lock position on the numeric keypad (the one with the symbol of a square with a cross through it) before trying to use the keypad; not pressing this button resulted in the numeric keys moving the cursor instead. I don't have an Intel-based Mac to confirm that this will resolve your issue but it's worth a try.
