Clearing those caches still seems to have done the trick.
In fact, earlier today I showed a colleague with a new MacBook Pro running Lion how to do that, and it likewise cleared up a whole bunch of problems he was experiencing in Word and Mail.
I'm happy, although still mystified, that clearing those caches has apparently turned all the tricks that needed turning, but just remember that trashing entire cache folders willy-nilly has the potential to cost you data and/or settings that not only most likely have nothing to do with your issue but may be a major nuisance to recreate.
