That's one reason why I play with AI off. As to the Copper Coronet I had a similar situation once due to careless use of pre-knowledge and doing things in the wrong order, resulting in having to re-load an earlier saved game (of which I keep industrial quantities).
This happened to me every now and then in the original version of the game. As Dunbar suggests, reload, also I'd recommend not assisting Hendak in killing Lethinan (also, kill all hostile guards first); thats when the neutrals used to turn hostile to me.
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