I could well be wrong about the name, you could try temporarily turning the indexing off if nothing else it would eliminating it as a suspect.

Whilst this delay is going on is the avast icon rotating ?
If so enable ‘Show detailed info on performed actions’ in the standard shield provider this should show what is being scanned.

http://img.photobucket.com/albums/v325/for-dwr/ShowDetailedAction.jpg