You should check and see if you have any other antivirus applications installed, and if you do, try disabling/uninstalling them. If you still get a bsod I would uninstall AVG. If your computer stops crashing after uninstalling AVG, then you could try to reinstall AVG to see if that solves the problem. Finally, if reinstalling doesn't work you might want to switch to another antivirus program. Avast and Antivir are both good, free alternatives.
I have Vista+AVG and have not experienced any BSODs. I think there is a known problem with ZoneAlarm and Vista. I switched to Comodo for a firewall and that fixed my problem. The problem I was having was internet connection drops and browser freezes, not BSODs though.
Also, have you tried updating to (or do you already have) the latest version of AVG (8.5 ...)?
Occasionally my vista crashes and gets BSOD and stuff... like every 5 days it'll happen and then I have to put my vista disk in the drive and Reformat my pc using the "Vista Whole Pc Backup" (Ghost) type thing and just bring it to date.