I've had some issues concerning wireless connectivity with the Xbox 360 S. It is connected to my 802.11b/g/n router which is located pretty close to the console. However, it detected only 4/5 bars but still otherwise stable (instead of a full signal on my laptop) and it randomly disconnects from Xbox live, despite its proximity to the router as well as a stable signal.
Is it the console or the router? I can verify the router isn't at fault since I have other devices (namely my laptop and iPhone) that connects to the router without issues. At the moment, I'm using an Ethernet cord or online connectivity. The router is in a semi-enclosed area but still, no issues on other Wi-Fi capable devices.