You are off topic for the forum you posted to, which is dedicated to Microsoft Security Esentials Beta
You should contact Avast as it would seem that the removal of the virus caused a driver to the quarantined or removed.
You may want to try the Microsoft Public newsgroups here: http://www.microsoft.com/communities/newsgroups/list/en-us/default.aspx
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator