Help with Bt Yoyager 210 on X-box live
 

I have a Bt yoyager 210 router that i use for the internet and for going on xbox 360 live,The set up i have is via a ethernet cable from my xbox to the router and a telephone line the problem is i can be on my xbox for an hour without any problems then suddenly the red power light comes on and it cuts me off live and i cant get back on for ages xbox and bt are no help and im at my wits end with it