Following a similar incident on the European PlayStation Network last week, Sony has issued a mandatory password reset to some users as a "precautionary" measure.
A post on the PlayStation forums advises users experiencing sign-in issues that they may be required to reset their password.
"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," a moderator wrote.
Sony did not provide details of the activity it detected, so it's unclear if it's connected to the launch of the PlayStation 4. The PS4's version of the PSN is not yet fully live in all territories ahead of its November 29 launch.