First I'm an avast user and not an avast employee, so I speak from personal experience and not from a developers perspective.
That said, are these systems using standalone installations of avast (Avast Free Antivirus / Pro Antivirus / Internet Security/ Premier) rather than one of the business solutions ?
You are more likely to have a better idea of the systems involved OS, CPU, RAM, etc. and see how that compares with systems unaffected.