Why when i test my xbox live connection does it say its working, but it doesn't?

[Ginger66]

Recently I was logging in on xboxlive to play some matches on MW3, my xbox said it couldn't connect to xbox live. I tested the connection and the results said it was working perfect. Later that day I tried to play Black ops and it worked!! So i thought I would try to play MW3, sadly I got the same message as before.

 

[herbert]

How are you connecting to the internet? Are you using a wired connection, or a wireless (WiFi)? I had a console where a WiFi connection would give me occasional problems, so you would want to check that out.