When you say you closed the program settings, I assume that you clicked OK rather than any other button ?
There is most certainly something strange with your set-up as all of the things suggested before 'should' have resolved the problem, yet nothing we suggest has worked, assuming you followed those suggestions to the letter.
You didn't answer this question - What other security applications do you have besides adaware ?
Try rebooting into safe mode,
http://www.pchell.com/support/safemode.shtml, start avast and try disabling self-defence from there.
@ LethalBoy
A conflict with ZA wouldn't have this impact, e.g. not allowing disabling self-defence, though I have little confidence on ZA free (or pro for that matter).