Serious XBOX Live help

Hi everybody. I need some help with my 360 and Live. I play my 360 at two places: my grandma's house, and my house. I am having problems with Live at both houses. I have a wireless network at each house, and I connect my 360 through ethernet on one of the open ports. When I am at my house, my 360 connects at first, then drops the connection about 2 minutes later. When I am at my grandma's house, the router does not even recognize that I have my 360 connected. These problems all just started happening very recently. So I am wondering can anybody give me some help?Serious XBOX Live help
is your xbox modded and what kind of router do you have?

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