20" iMac G4 suddenly won't create an uppercase "t"

[Chris Fitzgerald]

WtF? My machine has been working fine for years, and tonight, I start getting warning noises when I hit "shift-t" for an uppercase "t". Shift works with every other letter, and I have already tried restarting and swapping keyboards. I also notice that I can get an uppercase "T" using caps lock, but not with the shift key. What the hell??????:???:

[Chris Fitzgerald]

A bit more information: both keyboards work fine with my other Mac, so they aren't the problem. I've already restarted twice, so that isn't the issue. Do I need to reinstall the OS, or are there some prefs I can trash first?

[Chucker]

Does this happen in a fresh user account?

[Chris Fitzgerald]

Does this happen in a fresh user account?

I'm not sure, since I'm the only user the machine has ever had. How can I check this (sorry for being such a tech newb!)?