FWIW, i have heard numerous reports of AVG and of ZoneAlarm causing all kinds of weird problems with Vista. Less so AVG. the probs with AVG were more of the extremely long startup times that seem to disappear soon as a diff AV solution is installed in its place. ZA has lots of issues they said they fixed. i went to a diff firewall when i went to vista and havent missed it. my connections work a LOT better without ZA. my advice is try the things listed above, and not necessarily be too quick to blame vista.
The guy above with the dv6xxx series said his worked stellar with Vista, and i have a DV5xxx series i installed Vista on aftermarket, and it runs FLAWLESSLY.
By the way, i have Vista ultimate on this thing, and with NOD32 installed this thing flies. from power on to usable desktop is about 47 seconds. Give a diff av a try, and maybe a diff firewall, and if that doesnt help, then a clean install of Vista. im hoping its an easy fix like just picking a diff firewall and AV program. NOD32 is really awesome. some of the best detection and cleaning rates, really easy on system resources both at boot and while running a scan, and its very user friendly. worth it. lots of good firewalls out there. comodo is good but the alerts are crazy bad. works great though. jetico is another good one.
Hope you get it fixed. regardless though, please write back and let us know if you get it resolved or not, and if you do, what did it.