Meantime, while waiting for a reply, have a look at this thread.
One user mentions pushing a reset button on the back of the main board.
Another mentions low power being the problem, and to leave it powered for a few minutes.
Simply removing the rear casing seemed to help another, but this all seemed very hit and miss.
Either way, it sounds like you indeed do have a dud board, seeing as most people’s work perfectly 100% of the time. If you can get your current one working meantime: BONUS!