lofty50,
just spent three hours with a client whose machine is displaying the same symptoms you are having.
It stops you accessing any virus-removal site - I tried NAV, McAfee, Sophos, Trend, AVG (Grisoft) and others.
Liveupdate does not work and NAV gets disabled soon after start-up.
Windows update are also not installing although all the right screens appear but the number of critical updates remains at 37. Tried to download an install Win 2k SP4 but that got cut off.
I have tweaked the startup process with a utility similar to msconfig.exe - removed anything that look suspicious. I scanned the registry for any clues. I ran ad-aware and installed Zone Alarm.
I scanned the system using Stinger in safe mode and it did remove a couple of minor worms and viruses but essentially didn't result in any change to the situation.
All to no avail.
I am currently scanning the disk using my PC and the disk as secondary unit.
My next option will be to reformat and re-install everything, including windows updates etc.
Will let you know if I find anything useful during the current scan I'm doing.
Charles