[Streicher]

Nice hack, but you have a little error in it:

if ($HTTP_POST_VARS['action']=="movedate") {
  $DB_site->query("UPDATE thread SET forumid=$destforumid WHERE $forumcheck thread.lastpost<=$datecut");
} elseif ($HTTP_POST_VARS['action']=="movelockdate") { 
  $DB_site->query("UPDATE thread SET forumid=$destforumid WHERE open='0'AND $forumcheck thread.lastpost<=$datecut");
}
  echo "<p>Posts moved successfully! It is recommend that you <a href=\"misc.php?s=$session[sessionhash]\">update counters</a> now.</p>";
}

must be

if ($HTTP_POST_VARS['action']=="movedate") {
  $DB_site->query("UPDATE thread SET forumid=$destforumid WHERE $forumcheck thread.lastpost<=$datecut");
} elseif ($HTTP_POST_VARS['action']=="movelockdate") { 
  $DB_site->query("UPDATE thread SET forumid=$destforumid WHERE open='0'AND $forumcheck thread.lastpost<=$datecut");
}