[Tom Henrik]

I don't remember exactly which button did it, but this is what I do know.

There are two ways of moving your character, either by the cursors or by the number pad (with Home, PgUp, PgDn & End). It was one of these buttons. You open the door and walk straight for it. The cursors however will not help you here.

I might be wrong, but this is how I remember it.
Good Luck!