I had the same issue...
Tried almost everything (disbling services, regedits, you name it...), except....
I was like: Surfing till my eyes are crossed and no-one a solution on my errors, trying to uninstall / reinstall AVG? I did the unthinkable (meaning: I never thought of it!)
I searched for: avg uninstaller... Et voila! Where do I find a tool for it? at AVG itself!
It's called
AVG RemoverRun the program and perfectly, everything is gone
If you need it you can find it at:
http://www.avg.com/download-toolsHope this will help others as well