Update: Robert Bowling has just tweeted an explanation of sorts for the mishap on PS3. Apparently, “The amount of players on MW2 PSN overwhelmed the PSN presence server which updates “what you’re doing” and is essential to parties.”
He also stated: “PS3 Status: Patch successful. Trophy Unlocks on PS3 now available in Single Player & Spec Ops. Adding more servers to meet MP demand.”
Original: Infinity Ward ‘s Robert Bowling has stated via Twitter that the “Trophy update” has been released on PS3, and should fix any issues. However, the update has rendered multiplayer impossible, according to gamers.
“It killed all multiplayer activity on MW2,” player True_Darknight told Joystiq, which basically had rendered the matchmaking useless.
The devs are currently working on a fix for that now, and Bowling has tweeted that PS3 owners can expect a “party invite update by Friday”.
Hopefully, that will resolve the issue, but until then single-player is the only option until the fix.