This is a pretty sneaky trick and allows you to get into a Lineage II castle (no matter that the doors are locked). This trick works in Shadowbane as well.
User your arrow keys to run at the door as hard as you can. WHILE you are running hit Alt-X to exit the game. When you log back in you should be inside the castle. Obviously, this will be an extremely useful trick to use to sneak into a castle being seiged.