I have a similar problem, but during the "Rescue the Gnome" quest. After I pulled the brake lever to stop the windmill, the screen fades to black, but the cutscene does not play. I can not skip the (presumably) missing scene by hitting the spacebar. I can hear Barcus calling for help, and a sound is playing when I try to open the inventory, but since the screen remains black, I can't do anything else but reload.