i promise, its not the connection.
free zonealarm
avast does not change connection... the firewall does that.
Remove avast entries of Zone Alarm and boot.
Next boot, allow connections.
Into the firewall settings, the following programs should be allowed to connect:
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe (avast! Web Scanner)
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe (avast! e-Mail Scanner Service)
C:\Program Files\Alwil Software\Avast4\Setup\avast.setup (avast! Update executable). This is a temporary file that just appears when an update (check) is about to launch, and disappears again afterwards.