Is the avast Outlook provider active?
Check if it's not listed as a disabled item.
Outlook -> Help menu -> Disabled Items....
The thing is, the Internet Mail provider should basically IGNORE all Outlook traffic if the Outlook plugin is enabled.
BTW there's a new version of avast (4.7.981) available and it has some fixes regarding compatibility with Outlook 2K7. I'd recommend upgrading to this version.
Thanks
Vlk