After you uploaded all the files - 6.5 has a big utility which actually processes the upgrade.
You've visit
www.yourforum.com/install/upgrade.php - and login, then it checks that you uploaded all the files, it'll make adjustments to your language files, and modify the database. You'd remember it if you did it, it's quite flashy and there are several steps. <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" /> But it's an important part of the upgrade. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />