the dc board inside might've fallen slightly out of place. open up the cube, and look for the board where the power plugs in. you might want to take it out, then put it back in again, and if that fixes it, it was just the connection (this can happen from jostling around like during shipping). if it still doesn't work, you might want to look for burnt-out chips on the board, because that could be your problem too. this could especially be the case if you've put a processor upgrade in there (it's hard to crank out enough power for the faster cpu).