Try booting Windows into Safe Mode (press F8 when it starts loading) and uninstalling AVG from the control panel. Reboot the computer and see if the problem goes away. If it doesn't, have you made any other recent changes ? If so, uninstall these too. If not, the technical details on the blue screen error message may give a clue as to where the problem lies (consult an expert).
Touche
November 2010