For some reason, Avast has taken a dislike to V19.0.3 on my Windows 7 system, and will neither install it nor run it- it just hangs in either case without saying there's a problem. The solution is to disable file checking for the EasyPC folders, which isn't ideal, but gets it running. Settings->Active Protection->Exclusions and browse to the EPC installation folder.
I had a similar problem a while back where Norton decided to completely delete EasyPC on my laptop and wouldn't let me re-install. Had to setup EasyPC as an exception.
We get these pop up from time to time, where security software suddenly decides that our software is not to be trusted.
Some of these are due to Easy-PC being specialised software that is therefore not installed in huge numbers across the world, thus meaning we don't gain an automatic 'good reputation'. However, most are purely and simply 'false positive' reactions which can be reported to the security software vendor to be resolved. We have three different anti-virus packages running on our systems and are confident that the software we distribute is free from infection.