Weird internet problem

WinXP Home SP2. IE6. I can get online and surf OK, but AVG and Defender will not update, neither will Malware Bytes, SUPERantispyware, or any other malware apps. I cannot open MajorGeeks, Spyware Warrior, and other support oriented web sites. But I can surf around Google, Yahoo, and major sites like HP, Intel, etc. So, it seems to me that there's a really "smart" virus in this PC or Trojan, or whatever, that is blocking support sites from opening, and is blocking security apps from updating. I turned off Windows Firewall thinking that maybe it had been compromised and it made no difference. I've run scans with every program mentioned, and removed quite a bit of malware, but my most recent scans have come up clean. HijackThis didn't show anything strange, and I'm generally really good at malware removal. I've tried IE6, IE7 (which has been removed), and Firefox Portable; I've reinstalled Winsock and the TCP/IP; I've flushed DNS, and released/renewed ipconfig 'til I'm blue in the face. I can ping just fine. I've run Dial-A-Fix and CCleaner on both the HD and reg. I've booted with Last Known Good Config, system restore had been purged and disabled by the owner months ago so there's no restore points.
So.... any thoughts?
Is it possible that a 'smart' virus can block certain sites known for helping people? Can it block AV updates too?

 

Yes, I believe so. I had the exact same problem over the weekend, apparently some kind of trojan associated with the XP Antivirus crap. I loaned my laptop to a friend and her kids got hold of it and did who knows what. I just went through the MG malware ritual and cleaned it up. I went through a web proxy ( http://www.proxyfoxy.com/ ) to get here and to the other sites to get apps and update modules for the malware apps that had them as their internal updaters were blocked also.

 

Look for alternate data streams (lads is good)

 

Thanks for the tips you guys. I don't know how many dozens of times I've recommended that somebody read and follow the MG Malware Removal Guide, and then I didn't follow it myself I guess I got 'too big for my britches' as they say out west. Anyway.... all is well :celebrate I ran ComboFix, followed by a reboot, and then ran MGTools, and while the PC isn't perfect, I can now surf the web normally and update all the AV/AM/AS apps I need to finish the job.

Thanks.