|125mb upload/download in 7 minutes is not an insignificant dataflow nor is it typical of an antivirus update.|
Q. Do you have windows update set to automatic? Which level service pack do you have installed?
Have you done scans for nasties including antivirus and anti-malware? There are trojans and other types of infection that are not detected by antivirus alone.
download and run hijackthis then visit http://www.hijackthis.de/index.php?... and paste the logfile there for analysis.
Goin' Fishin' (Some day)