Sony has issued a password reset for some PlayStation Network accounts today, following some "irregular activity." While not all PSN users are subject to the change, if you get a log-in error it means you'll need to reset your password.

"We routinely monitor for irregular activity, and if such activity is detected, we may sometimes reset passwords of affected SEN accounts to protect consumers and their account information," a moderator on the PlayStation Community forums (via Polygon) stated. If you've gotten the error message, you can visit the change and reset page to make the change.