First of all, some quests become inactive when you already have one of the same OR after you load a saved game. I kept on creating Quests with Altar's 100 Gildar cost quest item, and after a while, or after a load, none of the quests were triggering when walking on them.
Second, I got to the last stage of the Arena tournament, and then some level ups triggered after the battle had started, and then the battle got stuck. I'm not sure if the fact that a Henchman got killed (ie. wounded) at the previous round made the bug occur.
I reloaded and did the Arena quest again, but this time, after I completed the last stage and got my Midnight Stones and Curgen's Axe, I clicked on my army quickly and it crashed (Windows said the program had stopped responding) before I could save my Arena win. The dubug.err is attached, it did not create a crash zip.