Hi everybody!
I have the same problem - my internet was cut off after updating of Avast 6.0.1091 from free to trial pro. Removing of Avast trial pro and reinstalling Avast free did not solve the issue. To remove Avast I used avast remover from this site.
My OS Win 7, firewall Comodo Internet security (with antivirus turned off), brousers Firefox 4.0 and IE 9.0. I’ve being used Comodo with Avast for very long time. This is the first trouble.
I can connect internet only if switch off Web shield in Avast.

I need urgent help!