having same issue on Windows 7 Ultimate 64 bit and Windows 10 Pro 64 bit, when connecting using a remote client eg: TeamViewer or VNC as soon as I try to open any Avast screen I loose all mouse and keyboard control... I discovered unchecking the box labeled 'Enable Hardware-assisted virtualization' in the troubleshooting tab and rebooting solved the problem for now, strange but it does not happen on all the machines I help with, had 2 identical machines (win 10 pro) and only one exhibits the problem?
It appears there is a bug in this new release 17.8.2318 (3705)