Also, do you have one (or more) Animal Compagnons? They seem to trigger crashes too... If you use AC's, you might want to dismiss them before changing locations on the world map.
Sadly I would say you have some basic problem with save corruption. (It probably has to do with bad proto(s), but which and where is anyone's guess.) At this point, if you don't have a save that pre-dates the problem, you're probably best off restarting. Save corruption is not terribly uncommon in ToEE, and it does seem to exhibit on some systems more than others, so while I wish I could guarantee that everything will be fine next time, I really can't. Just keep all your save slots rotating, save frequently, and roll back at the very first sign of trouble.