Hello all,
I was having the same problem as most of you after installing Asvast 5 (couldn't connect; couldn't update; firefox connected to the net while IE wouldn't, blah, blah blah). I am running Vista 32 SP2, having had at one point or another: Mcafee, Comodo and Zone Alarm and, thanks to alot of you and your advice, I got all the uninstallers I could find to clear up any traces of said former FW's/AV's. YET STILL, I couldn't connect to the net through IE or update Avast.
Not sure if this will work for you but after having read countless forums and spending 3 DAYS trying to fix this (the Avast AV rating's just couldn't be pasted up-and for free) I found this little , itty bity thing that let Avast connect (at least for me).
Purely by accident I went into: Network and sharing (my LAN settings); clicked on view status then properties and LOW AND BEHOLD, there was an old, old setting for comodo still there from 2 years ago I had no idea was still active. Soon as I deleted it, Avast worked, updated (quite quickly I might add) the whole bit!
Again, not sure if this will work for any of you but I finally got it going! THANKS to all of you for the advice on how to clean up old crap from my "puter". I appreciated all I've read and plan on spreading the info wherever I can!
Good Luck,
Therobbie1