That's a definite bug--I know for a fact that all 3 of them open. Two of them are locked, but you only need about 75% Locks to open them, and the third isn't locked at all. Try reloading.
My own theory about the chests that ARE completely unpickable is that when they wrote the game, BioWare gave each lock a number from 1-100, that being its 'difficulty' rating. But some locks got overlooked, and rather than going back in and assigning Lockpick odds, BioWare simply tossed in the message that "This lock does not open normally.....etc."
I wonder if some of the "missing" items, like the Helmet of Charm Protection and The Root of the Problem, are behind those unpickable locks?
__________________
Volothamp's Comeuppance
Everything you ever needed to know about the entire Baldur's Gate series......except spoilers.
|