How does this happen? (spoiler)

[DaleWind]

Ok, In the Troll caves in C2, my Druid/Monk with 34 AC was hit by an ogre who rolled a 15 (bringing his totally roll to 27). Not only that, he also did 44 damage to me (not a critical hit, since he rolled a 15) even when I had my Great Brawler's Belt on (which means he hit for 66 damage). Have anyone had similar problem, or is this one more of those random problems with the game?

[Yuusuke]

It's possible to crit on 15, although I doubt that was the case here. A natural 19-20/x? threat weapon, with Keen, and then Improved Critical would bring the threat down to 15-20/x?. Maybe a screenshot would help, but it's obviously too late for that.

[Mathurin]

Doesnt matter. You can THREATEN on whatever the crit range of your weapon is but the number rolled + your attack bonus must still be better than the target AC. The only automatic hit is that of a natural 20. A goblin with an attack penalty would still hit a dragon with AC 43 if he rolled a natural 20. If you have a keen rapier and improved crit you can roll 12's all day but if your bonuses added to the 12 don't beat the target AC you've still done absolutely nothing. Id say the problem the Dalewind had was a glitch. Ive had a few odd problems like that every once in a while, like rolling 10 damage with a longbow with normal arrows, even though the bow wasn't mighty and it wasn't a crit. NWN does have some oddities like that.