As mentioned elsewhere in another forum topic, there's something wrong with the damage resistance that some creatures with the Barbarian class are getting. TNVW nailed it on the head.
I was doing the kobolds quest the other day, and when it came time to fight the boss, there was nothing we could do to him. Our mundane weapons, when hitting him would render the message "Your weapon has no effect!" in the status window, and even once I enchanted mine, I couldnt do anything to him.
Eventually, after using all of our healing, as well as a few bonus heals from a perplexed and generous Howland, we were able to put him down. The fact that we were able to do so without any extra assistance has led me to theorize that perhaps his damage resistance was incorrectly coded so that it resisted 90% rather than merely 10%? Ie. The inverse of what was intended?
Anyways, I dont know the code, all I know is that the Cowardly Kobold Leader suddenly became a battle hardened berzerker that would put any Viking to shame.