1. go to your hard drive storage and press 'Y' this will take you to your system cache. Clear it. Then go back into the storage and locate MW3. Find the latest update and delete it. Turn off your xbox and reboot. Once you restart the game it will automatically
redownload that update. See if that helps.
2. Do a connection test. See if your NAT restrictions are 'Moderate' or 'Strict'. This could create issues connecting to various players on the game. If that is the issue you will probably have to go into your router and open ports to support an open connection
to your console.
3. Do a simple reset on your router. Turn off your XBOX and unplug your router. Leave it unplugged for a full minute (this does a system restore on your router. Power up your console and then power up the xbox.
Hopefully one of these will do the trick.
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