wp-admin login problem

I’m running cPanel shared hosting platform and recently I’m getting many report on WordPress login problem. All sites are using either WP 3.5 or 3.5.1. Also happen randomly across different physical server.

The problem is all user can’t login to Dashboard. I’ve tried using
1) wp-admin forgot password feature.
2) Change password through phpMyAdmin.
3) Change to another email address through phpMyAdmin and use wp-admin forgot password feature.

All to no avail. I can’t login using any of the password(both generated by forgot password and manually entered).

No PHP or Apache error detected by cPanel. My best guess would be redirect problem but I can’t figure out which file is doing it.

Here’s an example site : http://www.hafizstory.com/wp-login.php

Any solution and idea would be much appreciated.
Thanks in advance.