CI 1.7.2: Session + Database: Log user out when double-click on any link of the site!

[eluser]Unknown[/eluser]
Hi there,

Recently, I've been set the task to work on user authentication -- Log previous user out when another user, with the same username and password, is authenticated. I've been using Session with database. It seemed to be working fine as what expected until I found the problem. It's logged me out when I double-clicked on any link of the site. It's strange! And I've got no clue about that. Has any of you had the same problem and solved it yet? Would you have any suggestions about one-session login only? Your help is really appreciated!

Thanks,