I take both "A" and "B", and the resultant $10,000.
If Mr. Lowell "predicts" that you will select both boxes, then there is nothing in box B. He clearly stated that the winner will get the contents of the box or boxes regardless of what he predicts. He will, logically predict that you will pick both boxes; you have lost nothing in the choice, and box A results in a guaranteed $10,000, but you cannot pick it without also selecting box B.
Box B does not contain the million dollars. Because you will get the contents of the box or boxes regardless of what he picks, then even if you select the empty box B alone, you cannot receive the million dollar check. Lowell knows this, and is banking on the audience member being confused by the terms of the deal. In this case, Lowell is not "predicting" the outcome; he's simply hedging his bets.
Or, was I completely off the mark? (either way, a guaranteed $10g trumps a POSSIBLE $1.01 million)