[Grendel]

if ($action=="showthread") {
extract ($GLOBALS);
        $users_t=$DB_site->query("SELECT threadid, title,postusername, dateline FROM thread WHERE postuserid=".$postuserid." AND forumid=X AND visible=1");
        while ($users_threads=$DB_site->fetch_array($users_t)) {
          $post[specialthreads].="<a href=\"showthread.php?s=".$session[sessionhash]."&thread=".$users_threads[threadid].'">'.$users_threads[title].'</a> ('.vbdate($dateformat,$users_threads[dateline]).')<br>';
$postusername=$users_threads[postusername]
        }
if (!$post[specialthreads]) {$post[specialthreads]='N/A';}        
  eval("dooutput(\"".gettemplate("usersthreads")."\");");
exit;
}

if ($action=="showthread") {
  include("./global.php");
extract ($GLOBALS);
        $users_t=$DB_site->query("SELECT threadid, title,postusername, dateline FROM thread WHERE postuserid=".$postuserid." AND forumid=X AND visible=1");
        while ($users_threads=$DB_site->fetch_array($users_t)) {
          $post[specialthreads].="<a href=\"showthread.php?s=".$session[sessionhash]."&thread=".$users_threads[threadid].'">'.$users_threads[title].'</a> ('.vbdate($dateformat,$users_threads[dateline]).')<br>';
$postusername=$users_threads[postusername];
        }
if (!$post[specialthreads]) {$post[specialthreads]='N/A';}        
  eval("dooutput(\"".gettemplate("usersthreads")."\");");
exit;
}

Works fine!
Now only the categories are missing. And then it's done and perfect and a great and useful hack!

Thank you very much again!