well, i can't imagine it's the keyboard itself. the key can't distinguish between the 0 and ). it's got to be software/OS related.
i just posted this in another keyboard issue thread - see if you can try it:
i believe there is a keyboard .plist file (can't check for sure since i'm at work on XP right now). if you can find it, rename it and restart your mac.
if that works, delete the old plist file, if it does not, you can either keep the new one or put the old one back.