solved the problem. i changed the last post routine in ubb_forums.cgi to this
# begin last post hack
if ($last_post[1] eq "000000"){
$last_post_username = "";
}
else { $last_post_num = &GetUserNumber($last_post[2]);
if ($last_post_num ne '') {
# get latest public name for latest post replier!
my @user_profile = '';
if (-e "$vars_config{MembersPath}/$last_post_num.cgi") {
@user_profile = &OpenProfile($last_post_num);
chomp($user_profile[15]); chomp($user_profile[0]);
$last_post_username = $user_profile[15];
if ($user_profile[15] eq '') { $last_post_username = $user_profile[0]; }
}
else {
$last_post_username = $last_post[2];
}
my $total_posts = $total_replies + 1;
my $page_num = '';
if ($total_posts > $vars_display{HTMLDisplayMax}) {
my $total_pages = int ($total_posts / $vars_display{HTMLDisplayMax});
if ($total_posts % $vars_display{HTMLDisplayMax}) { $total_pages++; }
if ($total_pages > 1) {
$page_num = "&p=$total_pages";
}
}
$last_post_username = qq!
$vars_wordlets_mods{last_reply_by}:
$last_post_username!;
} else {
$last_post_username = '';
}
}
# end last post hack
if anyone else gets this
edit: i think its a problem with the old "change username" hack i used, and with unregistered post
edit2: just making it easier to understand, i enclosed the code that opens the profile with an
if that checks if the $last_post_num variable is not empty. when i entered the forum, there were some guests posts in the last posts (which not appeared in the topic listing).