If you installed Rebel Galaxy via Galaxy you have already figured out that It did not create the necessary registry paths.

So you will need to fix that if you want to manually update (saving your self in the process a 1.7 GB download via Galaxy)..

First grab this pastebin with a mock registy entry which you will need to edit to correct the right path where Galaxy installed your game (i.e. replace entries of E:\\Jogos\\ with the correct folder, take care to keep the \\ instead of single \) and the Save game folder (replace C:\\Users\\Miguel\\ with your user name).

(you will need to copy the pastebin text into notepad or some such, then save it as rebel_galaxy.reg)

When you have the reg file, just double click it and accept the changes.

Then grab the two Updates in extras (GOG-2 and GOG-3) and install those in order.

In any case it's probably better to uninstall and install from installer untill GOG fixes the issue..

Hope this helps someone.