Infinity Ward has issued a patch for the PS3 version of Modern Warfare 2, which should solve the problem with Trophies in single-player and Spec Ops modes.
The developer also said that a second patch would be released "by the end of the week" to sort out problems with party invitations.
However, the PS3 version of the game is still plagued by multiplayer server issues, which are down to PlayStation Network itself according to the developer's creative strategist Robert Bowling, writing on Twitter.
"It's a server overload not a bug in the code. They're working to have servers back up ASAP," he wrote last night. "MP Servers gradually coming back online. Some users may still experience issues," he added a couple of hours later.
"Looks like it was the amount of connections at once that killed PSN. They're enabling 20,000 users at a time to connect now," he continued later in the evening. "I believe this is Sony/DemonWare's temporary solution while they work on fortifying the infrastructure." (DemonWare is a networking company owned by Activision.)