While playing an online game, the PS3 displays one of the following messages:
-An error has occured. You have been signed out of Playstation®Network.).
-Failed to install trophies. Please exit your game.
First, try to check the Playstation Network status by reading the latest news on SonyPlayStation's Twitter:
Note: At the end of February 2010, a major problem occured. Learn more about it here