Losing connection to xbox live help me please,,,,,

I have 1 xbox and 2 360's hooked to one router/modem,,,Ive had it that way for about two years. Ive never had lag on my end. About a month ago my 360 started losing connection to xbox live,,it happens all the time now,,mean while my other xboxs and my PC dont lose connection. What can I do,,?? I reattached everything and switched ports that I plug the troubled 360 in the router and it still happens,,I cant even stay in an online game,,help me please if you can. Thanks

Well I dont know what to tell you like I said im no tech genious I use this modem: Linksys 2.4 GHz Wireless-G Broadband router. It works real well no matter how much stuffyou pluginto itbut its moreexpensive than othher modemscost me about $230