ExecB5: Alright, I figured out what to do.
I had to talk to thaler, his dialog options were all gray but talking to him about salamandra was what I had to do.
Oh yeah, I remember that now... I got stuck there for a bit too. You have to actually notice a creepy guy hanging around outside Thaler's house at night, and then you have to talk to Thaler. But if you talked to Thaler BEFORE you noticed that guy, then all his dialog options are still greyed out, even after you find the creepy guy. It was a little annoying.
Apparently there are a few other places in the game where greyed-out dialog actually reveals new options, but I think this is the only time that the main story quests are dependent on it.