Thanks for the reply. I'm creating a new one and assigning it to a new variable.
Code:
$pmdm =& datamanager_init('PM', $vbulletin, ERRTYPE_ARRAY);
$pmdm->set('fromuserid', 1);
$pmdm->set('fromusername', "Geocodes");
$pmdm->set('title', $title);
$pmdm->set('message', $message);
$pmdm->set('iconid', 1);
$pmdm->set('showsignature', 1);
$pmdm->set('allowsmilie', 1);
$pmdm->set_recipients($recipients, $botpermissions);
$pmdm->set('dateline', TIMENOW);
$pmdm->save();