Have you installed the latest
patch? If so, was this before or after starting the game? There are friendly thieves in the Verdistis sewers in games started before the latest patch. If you did not notice they were green on the mini map and attacked, it could drop your reputation enough that people become hostile (they were removed in the latest patch to prevent this).
Are most people annoyed, and some hostile, or is it normal and hostile? Your reputation drops by 2 on joining the thieves' guild, but they would have to already be annoyed for that to turn them hostile. Are the hostile NPCs all around a single location, or spread out?
