Also have you analyzed your IP traffic? You can download TCPView from the Sysinternals web site:
http://technet.microsoft.com/en-us/sysinternals/bb897437. Then observe the activity for avastsvc.exe.

When you start your browser, you will see a lot of connections for avastsvc.exe. This will settle down to one or two connections for avastsvc.exe to port 80(HTTP). At this point, your CPU activity for avastsvc.exe should be less than 1%.