There was a problem connecting to the patch server.
When you start a network-enabled game, the PS3 system will connect to the patch server to check if a new patch for the title has been released. If the connection fails, the PS3 system will sign out of PlayStation Network.
Solution:
Exit the game and start it again.
If the game will not launch, attempt to connect at a later time.
For more tips and hints on using your PlayStation system, visit our technical support forums at community.eu.playstation.com.