I was having this problem with the NPC's in Nadia's store in Silverglen, every time I went near the entrance the whole town attacked me, and the update today didn't fix it. Nadia, Sebi and the guard in the corner were each -45 attitude to all my characters.

What I ended up doing was sneak into the back room with my party, open the door into Nadia's shop, and move the screen into the room just beyond the doorway turning it so that they couldn't see me. When Nadia and Sebi each walked past, while standing behind the screen (they can't see me so I wasn't KOS!) I was able to speak with them and open trade and give them stuff until they liked me again.

Possibly this same premise may work for others in a similar sticky situation.