Anyway, I discovered the following while trying to find a hack that would make my Mac usable without buying a new keyboard for it. Apparently, the problem was in software not hardware, and was fixed by turning the repeat rate way down, then turning it back up (in the Keyboard tab of the Keyboard & Mouse System Preferences panel). This fixed my laptop as well as that of a new aquaintance's from class. Hopefully, it'll help someone else, too!

