I just went to Junktown to buy some rope so I could get down to the third level of Vault 15. The things that happen there happened, and now there's a guard standing in front of the only door, and he won't move for hell or high water.
Aside from shooting the guard and getting my level three butt kicked, how can I get out of there and continue with my game?
It turns out that the problem was that Ian was standing in front of the door trying to get to me, which stopped the guard from leaving. Moving over to the other part of the shop caused Ian to move out of the way, which fixed everything (I robbed Killian blind anyway).
He didn't move the first time I went over there, so it may be that you need to save and reload the game a few times to make it happen.