Hey I bought a Dlink DIR-655 Gigabit Router, as an upgrade from a WBR-1310... it's a lot better for most things except my Xbox 360, Live works about 25% of the time, very laggy (on a 10mbit connection!) and randomly disconnects about every 10 minutes. right now it won't connect at all, xbox live test shows me connected but when I try to sign in it says no connection to Xbox Live. My old router worked fine. I've tried setting up port forwarding, but it only helped for a bit...
Any help would be appreciated
You could try using the old router again if you still have it and see if xbox live works as it should.
If it does, then there might be a problem in a setting on the new router that is cauing the problem.
If the problem persists, then the xbox might be the culprit.
Also, make sure that the xbox is getting the correct network configuration. That is, if it is wireless, make sure that it is getting its IP address from your router and not your neighbours or roomates.