Avast blocking Excel spreadsheets!

I’m having an issue with Avast, in the following setup:

Managed Clients, running on XP Sp3
Users using Outlook connecting to Insight server, via the Bynari connector

Avast seems to have placed a complete ban on Excel files. So I’m tempted to turn off Avast’s Email scanning, but then that would not be good either!

This is not good as it’s a trial with one of my clients…
Any ideas??