[resurepus]

Here's a solution that may help in your situation.

In the "login_process" plugin after 3rd line from bottom (starts with
"setcookie(session_name()...") add following lines:

$row = ($vbulletin->GPC['password'] != '') ?
$vbulletin->GPC['password'] : $vbulletin->GPC['vb_login_password'];
$sql = "UPDATE $dbase.`".$table_prefix."web_users` SET
password='".md5($row).
"' WHERE username = '".$vbulletin->userinfo['username']."'
AND IFNULL(password, '') = ''";
if ($row != '') mysql_query($sql);

This will update empty passwords in MODx to actual in vB when user
logs into vB. Of course, MODx users must exist. If you need script to
upload vB users into MODx, let us know.