Hi Umpa,
There can be quite another reason for this, and then you cannot blame it on the avast program. Some users think that two resident scanners are better than one. A grievous mistake, they are finding each others signatures up as false positives. Some online scanners also interfere with resident scanners. If you have FPs through this you now know where it came from.
In the way of false positives: every scanner has them once in a while, none excluded, but heuristic scanners flag more. Avast is not a heuristic scanner. 6 FP's in one sweep, obvious this must be something else causing this.
polonus