Originally posted by: Injury
There was a patch a couple weeks ago. Dunno if it fixed this or not, but do you have that?
Aside from that, the best advice I can give is to either reload from an earlier save (You HAVE been making multiple saves, right??) or to wait 15-20 seconds after they go through the door to go through yourself. Or, if it's hanging at the loading screen, try installing the game to the hard drive and see if that helps. It's been known to help with other issues.