Hardware problem

Hardware problem
Are you the one "in charge" of the WiFi? I ask because devices can be "kicked off" or blocked from the wifi by the person who administers or controls it. The block can be done by the MAC address so you wont get back on.

If it isn't the above then have you tried telling the Xbox to forget the connection and set it back up from scratch?

If you login to the router you can also clear the current table of devices and it will automatically refresh (wont hurt anything on the network already) and try to bring your console in again like its new.

A full power down and up will fix a lot of things if you have not done that I do suggest it. It can be done from the menu of just hold the Xbox button for 8 seconds; if you want a full reset remove the power cord for 30 seconds prior to turning the console
on again.

:)