I have the same problem and the people in playstation network say activision is the only one capable of finding a solution, no words from them yet, in the meantime i switch to xbox, they don't have that problem.
it may be a conspiracy from activision to playstation network because they didn't get all the new versions.
Thanks for the reply. I tried to submit a question thru the Activision site, but when they give you a list of games to choose from, COD4 isn't one of them, so I don't know how that's supposed to work. I couldn't find any other info on the site about emailing or something. Oh well, not my favorite game to play, but I did enjoy it
I am having the same problem with mine. Called Sony, said it's an Activision/game server problem, and to get ahold of them. Kinda disappointed that there is no answer/solution to the problem from Activision yet. Very disappointed that the game isn't even on the list to choose from when you initially try to troubleshoot on the website. I even tried to go to another friends house and it was the exact same problem with his. We even tried his game (thinking maybe my disc was the problem) and same result: Fatal Error. Thus deducing that it is not the console (my PS3 Slim is not even 3 months old yet), or the disc itself, but a problem with either the latest PS3 OS update, or the 1.4 update on Modern Warfare, or both.
Activision or Sony need to address this ASAP because this could possibly be a security issue as well. I honestly don't think it is, but these days you can never be too cautious. Especially with Sony's recent past with security flaws. That, and it's just downright frustrating. I absolutely love this game, and would really love to play it again soon. I almost erased my entire hard drive, and sent in the whole console back to Sony while trying to troubleshoot with them. But thank goodness I went to my friends house and tried his disc, or else it would've all been for nothing and come back with the exact same issue.
Activision: Please help us, because this is an issue that I'm sure many people are experiencing, or will experience soon.