Sony has reset the passwords of a number of North American PlayStation Network accounts as a precautionary measure.
The company's European arm did the same thing last week after detecting irregular activity on the network.
In a post on the North American PlayStation forums, a moderator said: "If you are getting an error that your PSN account password is incorrect, you may need to reset it.
"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.
"Please visit this page for details on how to reset your password: Change and Reset Password. Note that if you have access to the email address and Date of Birth associated with the account, you will be able to reset it yourself. If you are missing one or both of those, then you will need to contact us for further assistance."
Sony said this week that PS4 firmware update version 1.51 will be made available to European consumers on Thursday, just in time for PS4's release.
PS4 launched in North America on November 15 ahead of this week's European and Latin American PS4 release date of November 29.