Receiving HTML as Plain Text

I have been receiving HTML mail and been able to read it up until this week.

It is now being recieved as plain text, all HTML scripting instead of HTML format. Last weekend I converted the C: partition from fat to NTFS. The Exchange Databases are not on that partition. Just the Exchange installation directory.

Our Antivirus was seeing the script as a virus, when I disabled the antivirus, I received the message in script form (<\Title>) instead of HTML format

What can I do to start receiving messages in HTML format again?