There is great clusterfuckassery going on right now on the PlayStation Network, affecting fat PS3s. Sony is working on it and they hope to "resolve the problem within the next 24 hours":
We hope to resolve this problem within the next 24 hours. In the meantime, if you have a model other than the new slim PS3, we advise that you do not use your PS3 system, as doing so may result in errors in some functionality, such as recording obtained trophies, and not being able to restore certain data.
The latest thin PS3 model doesn't have this problem, but if you have a fat PS3, here's what you are facing if you turn it on:
• The date of the PS3 system may be re-set to Jan 1, 2000.
• When the user tries to sign in to the PlayStation Network, the following message appears on the screen; "An error has occurred. You have been signed out of PlayStation Network (8001050F)".
• When the user tries to launch a game, the following error message appears on the screen and the trophy data may disappear; "Failed to install trophies. Please exit your game."
• When the user tries to set the time and date of the system via the Internet, the following message appears on the screen; "The current date and time could not be obtained. (8001050F)"
• Users are not able to play back certain rental video downloaded from the PlayStation Store before the expiration date.
Keep watching for updates. [Sony]