Not allowed. You get to look into the second box only after you have chosen. And even if both boxes were transparent, the paradox is easily fixed. Omega shouldn't predict what will you do (because that's assuming that you will ignore the content of the second box and Omega isn't stupid like that) but what will you do if box B contains a million dollars. Then it would correctly predict that your friend would two-box in that situation, so it wouldn't put the million dollars into the second box and your friend would take only the empty box according to his strategy. So yeah.