Ah, sorry: I should have added that before I found that statement from Sony, I immediately ran downstairs, powered on my PS3, and attempted to log in to both my accounts, all the way through PlayStation Store login. I was able to log in with my normal email and password, so I was completely baffled what the notification signified. I used the web portal to change my password, and that went through as well. Then I looked up support for PSN and found that last paragraph.
Seriously, not my favorite way to wake up on Monday.