My Xbox disconnects my internet service.

OK I've been having this problem for the past 4 or so days and it's starting to get frustrating. Whenever I turn on my Xbox it signs me in offline from Xbox live and disconnects my internet connection from my network and all the internet in my house gets disconnected. At this point I'm prompted to test connection on my Xbox so I do and select wired connection option because my Xbox is connected directly to my router via Ethernet cable, then when I test connection I always get the same result. Being that my internet connection isn't working (because when I turned on the Xbox it disconnected), so at this point I usually have to turn off my Xbox to restart my modem so I can get internet connection back up. But if I keep my Xbox on while trying to reconnect to the internet it doesn't reconnect. I go to my ISP website to reconnect my modem and my router usually just reconnects on it's own after my Xbox is turned off. I have a Dlink dir 655 router and my Xbox is a fat arcade from march of last year (just before E3 and they announced the slim with built in wifi Xbox). I am also on a DSL internet service and my provider is bell Canada.
Any help is appreciated,
Nick.

Check for firmware updates for the DIR-655. I have the same router, and my internet connection remains stable when my Xbox is turned on. I believe 1.35NA is the latest firmware version available. Update if you're on a lower version and try again.

Yeah I updated my Router so ignore the other message, it didn't help my Xbox though I still get disconnected when I turn it on.

Just tried that and still didn't work, this one is really trumping my because if it were anything else I could fix it in a minute. This is killing me because in my house I'm the networking guy and it sucks finally having a problem I can't fix on my own. Anything else you suggest?