#1 - Sept. 12, 2011, 1:12 a.m.
Here is a screenshot: http://screencast.com/t/VFlVGl0vaf4g
Note that I have clicked twice to walk through the gate and my character can not get past it.
I have not attempted to recreate this yet, I'll update once I try if I can recreate the circumstances:
1) Walked through main entrance, for the first time.
2) Killed most of the people in the place, including unique.
3) Normal wand attack gate twice, nothing happens
4) Magic missile gate, it blows open.
5) Attempt to walk through, blocked by invisible barrier.
Hope this helps.