Hey everybody, I encounter this annoying glitch upon descending the stairs from the first to the second level.
The interface appears but the screen is black for a couple seconds, then I die on what seems to be the top of a wall in one of the prison rooms (precisely the one with the goblin king portrait on the wall).
I noticed that if I start moving during those seconds of blackness I can move across the level (it's pretty fun) navigating with the minimap.
I am trying to reposition myself at the bottom of the stairs leading to level 1, so to repair to the game's error, but I had no luck so far.
Any suggestions?

Oh no! You seemed to have spawned at a Forbidden Polygon. Since you're at the beginning of the game, it might be easier to just start a new game than to salvage your saved game.
Otherwise, try quitting and starting a new game, then loading your saved game. I've also experienced a black screen for a long time upon loads. I've noticed that his happens only after I quit and start the game again (it usually only happens in Arx or where there are a lot of NPCs changing positions before the screen can load). I don't appear dead when this happens. It's possible that a goblin spotted you and killed you in the mean time (I don't remember a goblin being by the stairs, though).
In case this happens again, what Operating System and version of DirectX are you using?

Thank you for your suggestions. I managed to solve the problem by re-installing the game (I had backed up the saved games first).