"This file is clean" avast virus lab perpetual message

Hello. Can someone help me please. I am running Avast Free Version 12.3.2280. About two weeks ago it was suspicious about a program I tried to start. I submitted it to the virus lab for analysis. Later the file was proclaimed as safe but the message is forever popping up to tell me every time I boot the PC. It’s irritating and I don’t know how to stop it. Any ideas please? Dan

Start with performing a clean installation of the latest avast version.