One suggestion would be to change the wireless channel to either 1 or 11, if you have the actiontec router, then open internet explorer and type in "192.168.1.1" in the address bar.  A username and password box will pop up (unless you changed it the username/password combo should be "admin" for username and "password" or "password1" for the password).  Then click on "wireless" at the top of the page.  Then on the left, click "basic security settings", select "1" or "11" for the channel, and go to the bottom and click "apply".  The other thing you should know about this is that the xbox is most likely causing the problem because it is using up all of your bandwidth (or speed) to play games online.  Xbox can take up quite a bit of bandwidth because of the technology it uses, so it is very probable that you just need to upgrade to a higher speed package.