Thanks. I confess, this was one time I didn't search first. I couldn't believe it wasn't a general outage since I never have a problem with my Blackberry.
I did steps 1 thorough 3 with no improvement. So I spent a couple of hours waiting for and working with ATT chat support, who were great once you made it through the queue.
I think there should be a Step 4 in the routine. That would be to completely delete your e-mail account from your Set Up Blacberry e-Mail BIS site. Then reinstall it. That seemed to do the trick.
I've had no problems whatsoever in the six months I've had a bb (except for two general outages), and I don't know what caused my problem, but it seems to be fixed.