It seems as if the latest EE patch broke Wyvern Crown of Cormyr. The game now always crashes when you try to enter the inside of Hawklin Castle from the castle grounds (after getting the quest to meet Sir Hawklin there):
Apparently this has been reported since at least December, but so far neither fix nor warning have been released.
I only own the GOG version which to my knowledge doesn’t give access to development builds (at least not if you run the game without client like I do), but Steam users seem to experience the bug, too, and the patch notes of 8193.6 don’t mention this issue.