Its all in the power up sequence.
Unplug the modem for a minute, not just turn off, unplug.
Once the modem is up and stable, plug the power into the router so it gets the IP address.
Once the router is stable, power up the computer.
That did it for me. I have a NetGear router. Go onto the Lynksys site and see if they have any helpful hints. The Netgear site had it all spelled out for me. Take a look.