Outlook 2007 on Vista Business

I upgraded Office 2003 to Office 2007 on Vista Business OS and I am now getting errors on arrival of new mail. Avast cannot scan message body. Error 80040605. Avast 4.7.942 still in trial status. Worked OK with Vista and and Office 2003.

Suggestions? Have restarted OS as well as Outlook a couple of times.

Thanks, Rob West