Boot from Linux and try visiting the same Microsoft websites? I have done a lot of de-virus for food money (college kid) but have never seen a virus that prohibits visiting Microsoft websites. I just spent about 6 months doing research on bot nets and virus payloads, one of the sub topics was AV effectiveness, Trend Micro did the best for its price (we only tested the personal usage ones). If you know the processes your computer runs pretty well you could go threw the bitch of manually disabling each one until you hit the one that usually isn't there (I believe mean dormancy on viruses was around 4 months to avoid detection) which probably wont allow you to disable it, download an app and go from there. If you send me a zip of the log files I can probably take a look of them in a few hours (I am stuck on the comp any way, motor cycle accident). Anyway first post, hope I can help.

O personal note, would shy away from multiple AV's, they tend to bog down system resources as you stated and the companies have a tendency to dislike competing software and do not try their hardest to allow for harmonious coding.

Least you don't have Vista