I was hit by this bug for the first time while playing my Avernii Campaign. after a 20 year war with the Audei I finally managed to get them down to their last settlement and seige it with a decent sized army. I played the battle the first time round and it took over an hour (no time limit) before I won and destroyed the Audei. Only problem was I crashed before getting that satisfying "faction destroyed" message on the campaign map.
I found this fix and played the same battle again a day later. This time I wasn't rewarded with a CTD, and I lost far less men, though since I've "Unified Gaul" my campaign has got considerably tougher, but thanks none the less!