Have you tried the fix described here?:

http://support.microsoft.com/kb/827349

Also, you mentioned that the Protection status for your Antivirus program has POP3 mail off. You might also want to check if the AV program has it's own plugin for Outlook. If so, it may function independently of the POP3 setting. You should be able to check by going under File > Options > Add-Ins.

-SW