--- admin/processqueue.php.orig	2010-03-02 15:07:19.000000000 +0100
+++ admin/processqueue.php	2010-03-02 15:06:53.000000000 +0100
@@ -684,7 +684,7 @@
                unset($running_throttle_delay);
              }
            } elseif (MAILQUEUE_THROTTLE) {
-             sleep(MAILQUEUE_THROTTLE);
+             usleep(MAILQUEUE_THROTTLE * 1000000);
            } elseif (MAILQUEUE_BATCH_SIZE && MAILQUEUE_AUTOTHROTTLE && $sent > 10) {
              $totaltime = $GLOBALS['processqueue_timer']->elapsed(1);
              $msgperhour = (3600/$totaltime) * $sent;