keyboard stops working randomly

I have a PS/2 keyboard that I continue to use (because I like it) and it's plugged into a USB adapter. Most of the time it works, but sometimes it stops working, usually when the Mac goes to sleep. It wakes up and the kb doesn't work.

How do I fix this?

Others have the same problem.

http://forums.macrumors.com/showthread.php?t=1203335