All users are set to Full Control on all hard drives and folders.
I checked the Appdata folder but its all set.
Which is not the default setting (normally, an user can only control his own folders) so, you must have changed it and, in the process, probably create the issue. Such permissions don't always automatically propagate in all folders just because you set the whole drive with them, some folders need to explicitly set.
Please do as asked, and explicitly set YOUR user name (not "User" or "All Users", but YOUR user name) with full control on the %APPDATA%\Virtuali folder
I did a reinstall of GSX yesterday with the same result.
This problem doesn't have anything to do with GSX, it's your permission which are not correct so, it's no use installing GSX, because the issue is not GSX, but your system, GSX can't obviously force permissions on a folder (it would be really something if it was able to do it).