There's nothing wrong in the installer or the updater. Even the previous bug which prevented to install into a folder named "GSX", has been fixed. I don't see how removing AppData\Roaming\Virtuali" and "ProgramData\Virtuali" would make any difference, considering you said you restored them.
The only possible explanation is, interference from another product ( antivirus, most likely ) blocking access either to those two folders, or to the add-on.xml. Another user reported his add-on.xml went read-only, and since we surely don't set it that way, it must be another program that did that.
If the add-on.xml cannot be updated, the program won't be able to find any of its objects (because we have an additional path now, for PBR), and nothing will work, with such errors at start of not finding objects which are surely installed.