NOTE: You probably need a wired connection.
First, launch BO2 offline. You won't be signed into the PSN obviously. If your game launches properly and does not freeze then try this.
Launch the game again while offline. Your LAN cable must be disconnected from the console. While you're in the MP Menu, wait about half a minute (or a full minute just to be safe). Connect your LAN cable to the PS3, you will see the "signed in" notification. You should now get into MP and play.
Let's get some attention and hopefully Treyarch or ATVI Assist responds.