I am still stuck with the screen going completely black with the GOG version :( fix enabled, screen goes black on game start, shows white crosshairs for a few scond and that's it ... you can navigate the menu from memory and leave the game that way.
Have u tried to activate the fixer when u already loaded ur savegame (ingame). I have GOG version too and i use the widescreenfixer from dopefish and then choose the gog version in the settings and then start the game. Then i load my savegame and then when iam ingame i activate, then i get black screen then i deactivate and then i activate again and then it works for me.
Try to activate and deactivate for a couple of times when ur already ingame.