Problems with session

[eluser]Unknown[/eluser]
Hello all,
I'm using bramme's auth tutorial to write a simple authentication system.
The problem is in XAMPP everything works fine when I logout, thus I'm able to see the login screen again. However, when using Debian 4.0 with MySQL 5.1 and PHP5 (standard installation) when I click logout I'm returned to the same page I was before logout. If I refresh it a few times, it cycles between the login page and the authenticated page. Any ideas why this is happening?

Thanks a bunch,

Razvan