This is a REAL long shot. I have noticed in the past and present that ALi keyboards bios chips and certain keyboards don't play well. This problem was most evident with KeyTronic keyboards. All kinds of weirdness would happen.

I know keyboard bios chips are hard to determine now-a-days (I think they're built into the CPU chipsets now). Are there any ALi chips on your motherboard? I know.... there is a very slim chance. Hey, I gave it a shot!