So, while watching the movie during chat last night, Meryl and I figured out the real reason for that disappearing log during the Uncle Harold scene.
Before Aguirre arrives, the log is, ummmmmmmm, erect.
After Aguirre leaves, it has disappeared.
This is clearly symbolic of Aguirre's effect on Jack.
Others? Any explanations for why the jars of peanuts re-stack themselves in Monroe's presence, for instance?