Help. Keyboard and mouse quit working after sleep.

It doesn't happen every time, but it's getting annoying. After "waking up" the computer (it will wake up when I hit a key on the keyboard) the keyboard and mouse quit working. My mouse is plugged into the keyboard so it's probably just the keyboard. If I unplug the keyboard and plug it back in then it works again. Any idea?

I'm running OS 10.2.6 on a 600mhz G3 Graphite iMac.

Thanks.