Hi BE, HG612 GUI Update.exe shouldn't be run on it's own, it won't do any harm if you do, it will just give the error you got.
When the GUI has downloaded an update, the GUI runs that program, then the GUI should close. That program then makes a temporary backup the existing GUI, renames the downloaded program to HG612 Stats logging GUI.exe, then deletes the backup and then runs the new updated program.
When you run it standalone it can't find the updated GUI file to rename, so you get an error and it restores the backup.
There was a bug in the version I released this morning which would stop it telling you about an available update on start up (but the help menu - check for updates worked), but it did work on the version I released tonight.
At the moment there are no release versions, so you will need 'Receive beta updates' checked to get any updates at all.
add a donate button to the help and about page
Now there's an idea, I may well add that at some point.