Huh, well I am not quite sure you helped yourself with that action... If you don't know much about Widnows registry, and you removed bunch of stuff from withing regedit, it could be that you just made a silent disaster regarding some of your essential system files. Cleaning those without necessary Windows registry knowledge, is not the best thing you could do. I appologize if you have some registry knowledge, but it seems to me that you just blindly erased everything you found in registry. Windows registry is NOT a trashcan, so we can erase everything we find connected to, in your case, IE and avast!... oh no... registry is more sophisticated thing that we all can imagine.
Also, I don't think avast! was responsible for your problems at all. You even said yourself that you uninstalled avast! or completely disabled all avast! providers and you still had the same problem.
The fact that you didn't uninstall properfly Norton antivirus and Kaspersky prior to installing avast!, tells us everything. Never ever have two or more resident antiviruses enabled in the same time on the same machine - golden rule ! They will literally "kill" each other. You should have uninstalled all those antiviruses completely prior to installing avast! or any other antivirus tool... same thing, same rule with firewalls.
Also, making system backups on regular basis would hel you a lot. Now, you have to go through all this trouble, and I'm sure if you erased some essential registry keys, and of course, I don't believe you have exported your latest registry file, now it may be that you just made even more mess. If you have performed system backup, you could just restore your system to one of your previous safe points and that's it. I make my system backup images with Northon Ghost on regular basis. Even if something goes wrong, in about less than 5 minutes, my whole system is restored to any of those safe points I made earlier.
Cheers !