The installer doesn't necessarily catch and report all corrupt files when they are extracted. There is a file verification procedure in the link I posted before.
IIRC, there are only a couple torches in Joram's cellar. Do the walls and floor appear to be displayed properly? How about the game menu? Can you see the mini map (hotkey M) or auto map (hotkey A)?
Sometimes having caps lock (or num lock) enabled can cause a problem going up or down ladders, etc.
