Just to show what I'm actually talking about, I uploaded some screenshots.
Screen shot 1: http://www.fortunecity.com/skyscrape...ages/indy1.jpg
This shows indy preparing to descent down the first stepladder, supposedly towards a new room.
Screen shot 2: http://www.fortunecity.com/skyscrape...ages/indy2.jpg
This shows indy just after descending the stepladder, and after turning around. As you can see, I'm at the bottom of the shaft, and one level up there is the hole to the next room. But no matter how or where or when I jump, I can't get into the next room.