D-Link DIR-615 :: Internet Activity Light Blinking Non-stop With New Comcast Connection?

I recently switched from a DSL ISP (Earthlink, Zyxel modem configured as a bridge, pppoE connect) to a cable ISP (Comcast, Arris cable modem, dhcp connect). Basically PC --> DIR615-->Cable modem-->Internets. With the old DSL the Internet activity LED (green, looks triangular) on the DIR615 blinked only when internet activity occurred. With the new Comcast connection it blinks non-stop about 5 times a second! Even if the PC is turned off it blinks. It stops blinking if I disconnect the ethernet cable between router and modem. The connection itself is fine, but if the DIR615 is doing something it should not be doing it might slow the connection down a bit, (or burn something out prematurely?)FYI, the Arris cable modem does not seem to be a router. It takes a cable connection from outside and provides a single ethernet cable and 2 (voice) telephone cables to the house.