Hey, does anyone else with Tbird 2.00.23 find that suddenly all emails arrive as plain text only - and no HTML?

I've checked the Options, the Configurations and can't find an obvious culprit.

One site suggested maybe my Antivirus (AVS 9.0) is doing it, or the Windows Firewall in Win7.

I researched posts carefully as well as the KB's on the Mozilla site.

I'm afraid I'm stumped.....