D-Link DIR-655 :: Dropping Internet Connection - Macbook And Cox Cable?

I purchased this router and a Motorola Surfboard SB5101U for my home network.  My current set up at home for devices connected to router are as follows:

2 Macs and 2 iphones - Wireless
2 Directv boxes, 2 blu-ray players and xbox360, Ethernet cabling.

The issue I am having is that everyday at-least 7-8+ times my internet will just stop coming through.  I never lose connection to the router it's self.  But I cannot load webpages/content on any of my devices.  They always show as being connected fine to the router though.  I have attempted to call Cox cable, my ISP, to resolve the issue.  And I am always told that everything looks fine on their end and that the issue must lie with the connection between the Modem and router.  The rep then walks me through a complete reboot of both router & modem and of course, the issue is resolved 100% of the time.  I am trying to fix the issue my self to avoid a $50 service call fee from Cox which could still not fix any issues at all.  Since I have done some searching and found some advice on making changes to the configuration of the router.  But time after time I continue to get the same issue.