I believe the cell in the Dwarven Halls that contains the forth treasure map requires level 5 Lockpick to open. While it would not be impossible to find 5 items with a Lockpick bonus, it could take awhile. If you find one item with that bonus and do not mind joining the thieves guild in Verdistis, you can get 2 more levels of Lockpick there.
Did you try tossing a teleporter stone into the cell? That probably would not work, but it is worth a shot.
You could also just learn Lockpick, get the map, then use
iZakaroN's SaveEditor (or from
Kiya's site, with description) to unlearn the skill and pretend that your barbarian broke the lock. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
You could teleport past the blocked door in the cave:
Teleporting Anywhere, via hex editor.
