Linksys Wireless Router :: WRT150N Internet Port Dead?

It has happen suddenly : Internet is not working through WRT150N, though it work when directly connected to the modem. So I think it is a router issue :On the WRT150N, Internet light is flashing fast for 2 seconds, then is off for 2 seconds, then flashes, then is off and so on, wether there is a device (computer, modem, ...) plugged or not, through the blue ethernet connector.And sometimes, Internet light stays off from power on, whatever is done with ethernet connexions (yellow or blue).
 
When connected to the blue ethernet Internet connector, my pc ethernet lights don't blink (nor the link light or the data light)I have try the 30-30-30 reset cycle. But it doesn't improve.I have tried the loopback test : connect an ethernet cable from the one of yellow ethernet port of WRT150N to the blue ethernet of WRT150 N.Sometimes, the light for the yellow ethernet port goes on for a few seconds, while the Internet light continues to flash. After a few seconds, both go off.Sometimes, as soon as the loopback is made, the 2 lights go off, and if a computer is plugged to the yellow port, the ethernet lights of the computer and the router stays off.But I can access to WRT150N through Wifi and I can access to the web management.