I actually had the same problem when I recently replayed this game. It was making me
I searched the net with no luck
. Since I did not find any info on this problem I figured that It might not be a real glitch. Loaded the game again and the thing you need to do is simply walk/run using the keys on your keyboard(it will not work, at least for me only using the mouse) in different directions until you'll finally make it. Dont let it drive you mad. It will work.
Cheers and best of luck
ON:Gabriel Knight 1
Still Life(RP),Post Mortem(RP),Black MirrorIII,Amnesia,Aura2(RP),AuraI(RP),BS5 The Serpents Curse