Ever since the forum upgrade, there's been quite a few of you who had issues with their browsers not keeping them logged in. While posting threads or posts, the forum would keep on asking for the login info over and over again.
In order to fix this, the best bet is to log out and to clear one's browser cache and cookies.
Instructions on how to accomplish this on a Microsoft Windows computer with Internet Explorer 6are provided here.
If you use Firefox on either a Windows or Mac computer, you simply go to Edit - Preferences - Privacy - Cookies - Clear Cookies Now and Edit - Preferences - Privacy - Cache - Clear Cache Now.
After successfully clearing both cookies and cache, try to relog into tPF with your user name and password. The "Remember Me" checkbox is checked by default, which should keep you signed in the forum on that computer permanently (unless you clear your cookies again).