Motorola SURFboard SBG900 loss ethernet connection

My Motorola SURFboard SBG900 worked fine for over a year. Last night it lost its Ethernet connection but maintained the wireless signal. I have reset it a couple of times to no avail. I finally tried the USB connection. That worked but dropped my speed down from 100 to 12 mps. Is the modem defective or is the problem somewhere else?

Thanks for any input.