Aha! Finally figured out the interface. The "waiting..." message was a red herring that vanished once I selected a "destination" of Cassini itself.

[20 Minutes later]
Auntie nanila, you're *mean*! You woke that poor little probe up at 4:20am and made it do summersaults *all morning*! It's a wonder the poor little mite didn't throw up or pass out... =:o>