Suspected Logic Board problem (Command key held, even without keyboard)

I'm having an issue whereby the OS behaves as if the command key is being held.

First thing I checked was the keyboard obviously, so I turned it off completely to eliminate it, but the problem still persists. There is a significant performance hit too, as if all the RAM is being zapped by the issue.

I've taken it to the Apple Store, and they've reinstalled Lion cleanly, and I still have the issue.