Numeric Keypad 1, 3, 7, & 9 keys produce a "bonk" noise when pressed

[Think]

I'm using a Windows keyboard with numeric keypad hooked up to a Mac Pro. When I use the keypad to type numbers into applications, whenever I hit the 1, 3, 7, or 9 keys my mac plays the sound labeled "Funk", waits a few seconds and then plays it again. It seems like there is some 'feature' that is activated but the computer provides no information other than the sound.

What is causing this and how do I turn it off?

Thanks!

EDIT- The number keys work fine, they output the number I press, but those particular numbers also produce the sound.

 

[Think]

Ok, think I figured it out, (for those who make it here via search):

It appears to be my keyboard's fault: I'm using the Logitech MX5500 which is not officially supported for MAC. When you press any key on the keypad the keyboard appears to wait a couple seconds and issues another command - ???

Not sure what it's doing exactly, but the problem goes away when I switch keyboards.