Hi well its a customers pc I am a pc tech have been since 1990 its a old p4 The only reason i changed from 4.8 was there key ran out 4.8 worked fine. I have just not seen this happen before. If it works when its connected to the net it seems to me the program is looking for a internet connection before it works, to bring up the ad for the pro version as you dont get that ad when you are not connected. I dont see it being any other av on the system as the system was cleaned and yes you should only use one av program. So if the main avast interface works fine when the pc is connected to the net but does not work when not connected I dont see it being a previous av program or any program.I also cleaned the pc with malwarebytes before I installed the new avast.
MSI Mpower Max, I7-4770K, MSI GTX 780 Lightning, G.SKILL Trident X Series 16GB DDR3-2400, 2X Kingston HyperX 3K 480GB , 1Tb Raptor, Creative ZXR Sound, 1000 watt Coolermaster Single 80 amp Rail, G700s Mouse, Z5500 Speakers