Virtualized process reverts to being un-virtualized!

I have added iexplore.exe as a virtualized process and it initially works fine, but when I launch Internet Explorer a day or two later I noticed that the colour border is not present.

When I check the settings I notice that iexplore.exe is no longer showing in the list of virtualised processes. I only virtualise iexplore.exe, nothing else.

This has happened on a frequent basis over the past weeks. Avast IS version 2014.9.0.2011

Is this a known issue and what us being done about it please?