I had the same problem when going from Hydlaa plaza to the arena. Every time quite the same spot, very close to the end of the tunnel (had the problem from the other side, too).
Robzombie179, did you buy any armor in the game? I bought a pair of leather boots, but sold them soon after (i read they are not implemented). Someone guessed there could be a connection.
Another hint might be the camera - when using a 3rd person view and standing near the tunnel entrance, i can sometimes see the scenery from outside, where you could never go to.
Perhaps the camera gets to a spot that it can\'t show or something?
I once was able to avoid the crash when moving to the tunnel in 1st person view. I don\'t know whether it will help again, tho.
edit: Problem is solved - well, evaded - now anyways, but i just want to add that it could not have to do with the camera as well. At least it could not only be the cameras fault, because the crash also appeared in 1st person now (see next reply from Game Master zabeal for reason).