Thanks, but had already tried that.

After posting, I tried several other things and finally found the fix. Under
"Tools |Templates and Add-Ins...", the dialog listed the template filename in
the "Document template" field. It was not the "Normal" template. I cleared
that field and hit OK, and do not get prompted anymore. On returning to that
dialog, it shows "Normal" in that field now. Maybe that will help someone
else having the same problem. Thanks again.