I have Windows Vista Home Premium and run ZA Extreme Antivirus and Firewall. Man, it's great. I love it.
This not a ZA problem, it was mine.
For the second time this year I got virused and had no internet connection, only blank pages. The first time it took me about a month to get it fixed and all re-updated by reloading my Vista. This time I did much better, it only took three hours.
This had to do with a fake Adobe settings.sol program. The settings.sol is required to watch videos on most web sites. A site I was at said I needed to update to a newer version and so I did, without scanning before installing. That was all it took, I was off line.
I did an advanced pc search for the day and time involved and found that hidden and non-hidden Pbk's had been changed. I was surprised that no TCPIP's were involved. I opened all the Pbk's with WordPad and deleted everything in them and then shredded them with my CCleaner. Next I did a system restore from a previous date and all was and is well. I now scan and create restore points more frequently.
Hope this may be useful to someone,