This just happened recently. I just got into Sciropescire and have been doing a bit of exploration and just realized when I ran into the Zealot in that area, that nothing is attacking me. I knocked the Zealot off his horse and he just stood there and let me defeat him. I thought it was a bug, but now when entering other places where guards are, they are not attacking or agroing me. Even if I attack them. They just stare at me and stand there or continue on marching off somewhere.
