I´ll try to explain in few words.
As you can see in the images, an enemy troop is blocking the access to the elevator. I can´t flank them, neither combat them, because it´s as if they just were a wall which I can´t pass.
http://img39.imageshack.us/gal.php?g=bugddd.jpg
I bought game on Steam (updated to last version) several days ago and I´m simply loving it. From the marvellous OST to the wide variety of places, enemies and ways to play the game. I just hope this bug doesn´t ruin my actual game if I must go through that elevator for main quest.
Thank you in advance and waiting for a possible solution.