Make sure you Xbox still has the same assigned IP address. I know mine will change from time to time. For example, when I got a DVR, I connected it to the internet. For some reason the router decided to make it 192.168.1.104, the IP address my Xbox had been. Now my Xbox is 192.168.1.107, so I had to change the portforwarding settings to reflect this. Also, make sure the following ports are open 53, 80 to 83, 87 to 89, and 3073 to 3076.