Sony isn't having much in the way of luck lately. The recent return of the PlayStation Network has been short lived as a new exploit was discovered to compromise the PSN password reset page.
Reports on NeoGAF and Nyleveia suggest that the account password can be reset using only an e-mail address and date of birth. Through personal data available to the hackers in the initial attack on the system, hackers can hijack existing accounts by simply cross-referencing the information.
The issue was reported on NeoGAF, where users successfully managed to compromise their accounts.
Sony has since taken down the system in the wake of these reports, presumably to implement changes.