For what exactly?
Theater? When you're trying to access the MP main page?
Just to make sure:
1. Is your NAT type OPEN?
2. Is your xbox behind a firewall(via router or through host's connection via AD-HOC)?
3. When did this start?
4. Did anything happen to your connection from when it was working to when it was giving you the error? This can include power outages, surges, breaker shutoff, fuse replacement, etc... pretty much - was the router turned off?
5. Are your ports forwarded? Is DMZ mode on if supported?
6. Is UPnP turn on? QoS?
If all else fails, try doing a power cycle on your router. unplug the router fully, then hold the power button / reset / refresh button down for 5 seconds. Replug all connections and the power cable.
Hopefully one of these things solves the issue.
I was playing online, and now i cant, i am allways receiving this error code.
The 360 conect's to the net, and then sudently turns off, and gives this error 312...
I have made 10% of the online game, and now i cant even conect to your servers..
Just done a google search and all it seems to be is an error while trying to fetch your profile from the cod servers, just wait a bit and it will sort itself out.