This is an issue which HMX should have taken care of before Lego Rock Band was made available as an on-demand purchase. That being said, they are not the publisher so it's entirely possible they weren't even aware that the game was being brought to on-demand on xbox live marketplace...

...Anyways hopefully this issue gets fixed as soon as possible. I'm aware that it's cheaper to purchase Lego Rock Band directly from a store but on-demand buying is just so effortless.