Thanks for the offer, Kathleen! I agree--a wipe is pretty drastic. The error
message was one of those "The meessaging interface has returned an unknown
error..." messages, and I couldn't find a fix doing a Google search.

Fortunately, a System Restore took care of the problem, which I think was
caused by the new Google Desktop beta. Hopefully, the next person with the
problem will come across this message and try the System Restore before
nuking their computer.