I have good news for you! I had exactly the same symptomes like you. After a few days of investigation I have found that the power supply is faulty. It can not provide enough current to the device. The standby voltage is 5 volts, and the maximal current is 2.5 ampers (at least it is stated by the sticker on the power supply). But it seems that the device needsaround 1.5 ampers during the boot sequence, and some more if you use the USB connectors too.
So if you buy a stabilized power supply with 5 volts nominal voltage and 2.5 ampers maximal current capability, you can use your router again, just like me.