Wow, that is terrible, I am really sorry to hear about this.
I once had this happen in part 4, he just wouldn't come down. It was a Sunday afternoon and we waited about 15 minutes, but eventually a GM responded and unstuck him.
What bothers me in this GMs response is that he didn't seem to provide any reassurance about what he COULD do, only what he COULDN'T do. This is rule number one of customer service. Heck, it's rule number one of just about any job. Own the problem. Make it your personal responsibility to figure out what you can do to correct it, and then do it. If he tried to unstick him and it didn't work, well fricken try it again. If there is absolutely NOTHING you can do, at least tell the poor schmos what you tried. Tell them, I am looking at the boss and he appears to be unstuck, but is for some reason not advancing. I am sorry but there is no way for me to advance the quest from here.
DDO has some of the absolute worst customer service that I have ever experienced. The complete lack of any communication, or reassurance, about what they can and will do. It's disgusting.