I just installed the quickstart and check that the PHP requirements were fully satisfied during the initial setting process. The site displays properly, but for some reasons I cannot login to the admin back-end. The username (admin) and password are not recognized. I re-did the installation three time to make sure that there was not typo in the password. I am using PHP 5.3.14. I tried installing the quickstart on two different servers, but had the exact same issue.

Do you have any suggestions?