Today I ran the updater again (as admin). Bad idea. The same error popped up again right afterwards. I gave the updater another shot (this time without admin privileges) which updated another few pye files and everythings worked again.
The updater will ALWAYS run with Admin
privileges, so there's no need to do that manually. However, if you do that manually, it will be run by the Administrator
user, which is not exactly the same thing as running with admin
privileges on YOUR user name and, in fact, might cause problems, since the Administrator
user account wasn't the one you originally installed GSX, so it's missing all its own registry keys, confusing the updater when run this way.
But it wouldn't be very right to always use Admin registry keys to install into, even when running from another user account, this is usually considered a bad practice.