While logging in just tick on the Remember Me box and it won't happen. And do it in your personal computer only.
I had this problem even when ticking the box. Either clearing cookies manually or when you login hit the logout button before your automatically logged out to clear cookies. Well, if we were/are having the same problems though this might help.
Come on man.. there's a similar kinda thread on the 1st page itself!! http://forums.digitalpoint.com/showthread.php?t=48315 Go explore.
Click the actual log out link and then log in. If that doesn't work, then something inbyour computer is deleting/editing your browser cookies.