wireless keyboard not responding after sleep mode

My Apple Wireless keyboard (old style with numeric keypad) does not respond properly when my computer exits sleep mode. Keys either don't work or a single key hit produces multiple letters / numbers on the login box. The only way to get the keyboard to work properly is to turn it off, wait until the computer says it's lost the keyboard connectilon, then turn the keyboard back on again.

I tried a newer Apple Wireless Keyboard (current model) with this computer, and it works properly.

Anyone have an idea as to what's going on here?

Thanks