Xbox Live problem please help!!!?

Alright I cant connect to xbox live, when I troubleshoot it, it says that the MTU setting on my router is set at 1364 but my original setting is at 1492 so I went to my router configuration webpage and tried to change the MTU setting to 1364 but it goes back to 1492. If you know what my problem is please dont hesitate to answer, this is seriously pissing me off, Xbox Live worked for a very short time, enough time for me to make a gamer tag and then I went to play a game and it Fu#@%^ up. My router is a Net Comm and I got it from Adam internet for about $50.00