If you are still experiencing this issue, here are some tips you may want to try.
You can always check online services status here http://www.callofduty.com/ghosts/status
Currently the status is at Defcon 4 so you may experience intermittent issues with connecting to the server.
You may wish to check Xbox Live service status as well Xbox Live Service Status - Xbox.com
If online services are fully operational and you are still unable to connect, you may want to try the following.
- Reboot your router.
- Restart your system.
- Try using a wired connection in order to sustain the connection quality.
- To help identify if there is an issue with the router or blocked ports, try connecting directly through the modem.
- Establish a static IP address and port forward.
Here are the port numbers you will need:
Xbox 360: Activision Support
Should you have any questions on how to port forward, please contact your ISP or the router manufacturer.