writes "The Sony PlayStation Network appears either to be down, or inaccessible to older ("phat") PS3 units. Players cannot play games that require a connection, even in single-player, offline mode, e.g. Call of Duty: Modern Warfare 2. Also, the system date resets to January 1, 2000. Sony is "working on it ..."
Speculation abounds that it is a bug related to 2010 being a leap year."Link to Original Source