From what I know it could mean either. This once happened to me long time ago however there was no changes in my purchase history or my download list so I know no one caused any trouble but may have attempted.
It was originally reported not too long ago that Sony suspected a breach of the PSN to several accounts and reset their passwords just to be safe before too much damage, if any, was caused.
As a good tip, make sure your new password is very different from your old one and change any other accounts that share the same password (e-mail, Xbox Live, Nintendo Network, Facebook, your online login to the that one cooking the perfect meat pie message board, etc.)