After playing some time using this mod, I found that I don't like Quayle that much after all. How can I revert to Aerie, without replaying the game from an old save?
I stumbled on the same error. Very hard to find out, I didn't notice Berrun approach until several hours later. But I keep playing now, just kill Berrun (before he talk to you, of course) using <Ctrl><Y> and the games seems to working fine again.
Previously I had to kill the same way a high level magician, Rhialto, that attacked my party several times after resting, killing everyone. He was supposed to convert himself on a squirrel (a wild mage), but he did not.