The Dec. 3 update of Avast 4.8 had a BUG.
It was reporting a LOT of FALSE positives. It claimed System Mechanic 9.5 was a trojan. I checked the Web. Others were having same problem around the same time.
Yes, there were reports of the false trojan problem on the Avast Forum.
While I was checking this, Avast said I had a new update. Installed that. It now seems cool with System Mechanic.
I saw a ‘similar’ false positive scare with Avast two years ago.
Be careful for the next few days. I will keep you posted.