Guards attacking on sight in Nashkel

I have a problem: the guards in Nashkel attack me on sight, even though my Reputation is 13, and it says that I am Popular (my character is a Chaotic Evil Half-Orc).

I think it might have something to do with something that happened at the start of the game, when I tried to force open a lock, and someone saw me; I killed the guard, and now I'm hanging around wearing his armor and stuff, but I have been a good boy since then.
Is this some kind of bug? Should I restart the game?

EDIT: I donated 1.5k gold to the temple next to the Friendly Arm Inn, my reputation increased to 14, I went back to Nashkel, and I'm still being attacked by the guards. Is this because I'm playing a Chaotic Evil character?

Solution 1:

I think it might have something to do with...

Exactly.

The fact that Flaming Fist soldiers will spawn and attack you at very low reputations (much lower than 13 - i think less than 5) has nothing to do with this.

Once you make someone hostile, (even a Nashkel guard), they will stay there and be hostile forever. You made them hostile once, there's no way to un-hostile them, even if you get reputation 20.