I was so into the main quest line - chasing down High Kinlady Estre all across Auridon, and righting her wrongs along the way. Finally we had cornered her in the last Oblivion portal, and were about to cut her down when...
I zone into the area and am immediately notified that I have completed the quest. What a disappointment! All that chase only to have a bug take away the final fight.
I really hope that this kind of bug is fixed quickly, because I can't even look at this game right now (and I am really really enjoying it)!