The time on Make Your Move when the contestant wouldn't make a decision and Bob had to play the game for her. Looking back on it, I wonder if the lady was unwell.
I think on this one, this contestant simply did not have a clue as to how to play the game, despite Bob explaining it about as thoroughly as he could. I've seen the clip and she seemed to have a deer-in-the-headlights look, and she seemed to be looking to the audience for someone to help her.
Sometimes, this happens ... and not just on game shows: You explain something to about the simplest of terms and they still don't understand. A non-game show example might be "Homer's Triple Bypass," where Dr. Hibbert is explaining to Homer the heart surgery they are going to perform on him.
Which leads me to wonder: How many game shows has this been the case, where you explain the rules and they either are completely clueless or, perhaps they say they understood what they were just told and then they prove (by their gameplay) they really didn't?
Brian