SPOILERS
Here is one, though I doubt you'll believe me. I haven't still worked out
what the hell happened!
Imoen got a wild surge! That's the unbelievable bit. Next, she did it during the final battle. I had ToB installed, so it was possible, despite the fact Imoen isn't a wild mage. Anyway, I was fighting Irenicus and she tried to cast 'Stoneskin' but, instead it did a roll twice. She summoned two Pit Fiends!!!! It was a pain, considering I hadn't been protected from evil!
And another one. I was doing a wild mage solo, and in a battle with Irenicus at the end of ToB (Ascension Mod), I turned myself into a wolf! I couldn't cast spells and I died.
I still don't understand why Imoen could do wild surges......