According to the manual a blinking amber Modem Status light indicates a problem with the modem (cable modem or DSL modem).

You might want to try upgrading the firmware on your router if you have not done this yet. (page 57)

Also, make sure that the ethernet cable from your cable modem is connected to the YELLOW port on the back of the router.

http://cache-www.belkin.com/support/...01122_7-08.pdf