Same deal for the rear. You gotta think of everything. It could be how the wheel is held, not the wheel itself. Front or rear, doesn't matter, it could be the dropouts. Last time I had a problem like this I couldn't figure it out with the customer over the phone, but when he brought the bike in, the dropout was all munched as he had been riding with the wheel loose for so long. He would do it up tight, but when he jumped or pedalled hard the wheel shifted in the frame. Bearings were fine.
thats a good point. it might be the skewer, drop out or the mech hanger thats damaged, all of which would prevent the wheel from being properly tightened and fixed.
theres nothing simple about bmx hubs. externally its all just bolted on, but the internals of a quality Profile hub are just as complicated as anything you'll find on a mountain bike.
anyway, take the wheel to a good shop, explian whats been happening and they will know what to do.