I hate to bring an old thread to the top again, but I think I have the same problem. For me at least, it seems it happens right after the Labyrinthian quest for the College of Winterhold. This is the second time (second character) this has happened. Up to this time, never had a problem running through that area, but right after that quest, as I am running back to Whiterun to offload some goodies I collected, I get right around the Nordic ruins where the bandits are, if I run through that area, I will get a CTD, or at least a major slowdown in video frames/minute that will cause a CTD if pushed any further by running. If I face West, and walk backward, I can make it through with no problem, but if I turn around and face east, the video gets extremely slow (1-2 frames/second). I can maybe walk through the area, but that is a total waste of time. Right after it happens, I try to avoid the area like the plague and walk around it, so it won't happen again (Though there was a quest to kill those magic anomalies that had me trying to enter that area walking backward) so I really haven't done too much trouble shooting to find out what it is, but there really isn't anything in the area that changed that would make me think it was a certain mod I added. I do have SKSE installed, though it seems to work everywhere else with no problem, even up to the quest mentioned above, so I doubt this is the problem. I don't have any mods that modify that area except maybe for the Climates of Tamriel mod, but that was mainly for weather changes, not terrain changes, or whatever is causing this. I have a Geforce GTX 690 video card, so this should not be a the reason for this. I have all DLC, and all Unoffical patches for those.