I am on the Quest "Enter the forbidden zone dome." I have found the entrance problem is when I enter my player is spawning under the walkway. I have tried several times with the same result.
http://img.photobucket.com/albums/v222/Crow_ASP/ScreenShot8.jpg

Since you are on PC, you can go into the dev console (press the tilde ~ key) and type tcl to turn off clipping. You should be able to move out of that. After you're out, type tcl in the console to turn clipping back on.