My game has locked up in only two areas -- the transition entering the Balinoks from the north (Vallaki), and the transition coming out of Dvergheim. Each time it is when I am attempting to enter the map, and only from those two transition points. The map generally loads correctly, then freezes when I attempt to move more than a few paces. Interestingly, I have found that if I initiate movement very gingerly in those areas (i.e. I don't change camera angles, I move only using mouse-clicks, and only a few paces at a time) once I get a significant distance away from the transition points, I don't have issues.
My solution for lock ups has been to exit the game, reboot my computer, restart NWN, lower the graphics settings to "stupid", then everything usually loads correctly. If I don't reboot my computer, and just try to reload NWN (even with lower graphics) my game does not load correctly (I freeze during the loading).