My 4100b is flashing ethernet green and power

Hello I have the same modem and it had the same problem where it only lit the Power and the Ethernet LEDS. It is Quite easy to fix. All you have to do is Hard Reset it because soft resetting it wont do.
To hard reset it: 1. Hold the Reset button on the back of the modem for ~10 sec. until it resets itself. 2. >>Before all the LEDS disappear and only show power then Ethernet<< turn it off and unplug all the connections. Leave it unplugged for a few hours just to make sure that it goes back to Factory Default setting.
After that, plug everything in and turn it on.
Now, if it does not change and returns to normal. Press the Reset button while all the LEDS are lit then quickly unplug the 12vdc plug and wait.
If this fails, Search google for forums that mentions this similar modem ad same symptoms and see if they have a solution.
Hope it works, GOOD LUCK!!