call to a member function on a nonobject

[denniss]

I am trying to use a function to change a user's password and I get this error:

Fatal error: Call to a member function query_first() on a non-object in /usr/local/apache/htdocs/forum/includes/functions.php on line 1600

the function I am running is this:

function changepassword($newpw) {
global $vbulletin;
$vbuser =& datamanager_init('User', $vbulletin, ERRTYPE_ARRAY);
$vbuser->set_existing($vbulletin->userinfo);

$vbuser->set('password', $newpw);

if ($vbuser->errors) {
foreach ($vbuser->errors as $error) {
echo "<br> error: $error";
}
} else {
// no errors, so save new vbuser.
$vbuserid = $vbuser->save();

}
}