[Xenon]

open forumdisplay.php

find

PHP Code:

$forumusers = $DB_site->query("SELECT username, invisible, userid
                        FROM user
                        WHERE  inforum = $foruminfo[forumid]
                            AND lastactivity > $datecut
                            AND lastvisit <> lastactivity"); 


and replace it with

PHP Code:

$forumusers = $DB_site->query("SELECT username, invisible, userid
                        FROM user
                        WHERE  inforum = $foruminfo[forumid]
                            AND lastactivity > $datecut
                            AND lastvisit <> lastactivity
                ORDER BY username"); 


i think this should do the trick

by now it is orderd by userid