Well, I spoke too soon. Just as with my old router, everything worked fine for about 18 hours, and now, nothing is working correctly. I'm slowed down to almost dialup speed and cannot send email (SMTP times out -- can receive, though).
So, I'll spend another evening trying to reset and re-employ everything. AT&T says it's Linksys; Linksys says it's AT&T but no one can give me any answers. So frustrating when everything was working just Hunky Dorey for many years without a hiccup.