Users are having trouble staying logged in on the forum since the upgrade to PHP 5.3 from PHP 5.2.10. None of the cookie settings changed, as everything worked on 5.2.10 - here are the values of what is set, session wise:

Authentication: Db
Session Length: 36000
Allow persistent logins: Yes
Persistent login key expiration length (in days): 3
Session IP validation: A.B
Validate browser: Yes

I'm also using PHP 5.3's new mysqlnd, instead of libmysql. And for $dbms in config.php, it's set to mysqli