Medal of Honor released this week, and if you've yet to purchase the game, let alone update your PS3, you will have to apply firmware updates 3.42 and 3.50 in order to play the game.
In case you've been away on vacation or something, the firmware (Jailbreak killer) updates prevent hackers from running pirated games along with the use of unauthorized controllers via the USB ports on the console.
Medal of Honor, along with all games hitting the system from here on out are encrypted with the new encryption key, which means the current Jailbreaks out there for PS3 will not be able to read the code on the disc.
Digital Foundry explains it so much better than we can through here.
Still, if you haven't dusted your PS3 off in a while, and plan to do so, you'll need to update it in order to play almost anything from here on out.
You may want to make sure any off-brand controller you have for it still works too, once the update is applied.