could someone take a look at this script?

[kh99]

OK, looks like the problem is that you're changing $user['membergroupids'] and messing up some stuff that tries to use it later (a reference is passed to the function so any changes will affect the variable that's passed to fetch_musername() even after it returns).

So I would make these changes (lines in blue added, lines in red can be deleted):

global $vbulletin; 

/// NOTE - Make sure that the $user information includes the MembergroupIDs 
if (!array_key_exists('membergroupids', $user) || !array_key_exists('usergroupid', $user)) 
{ 
    global $vbulletin; 
    $tempuser = $vbulletin->db->query_first(sprintf("SELECT usergroupid,membergroupids FROM " . TABLE_PREFIX . "user WHERE userid=%d",$user['userid'])); 
    $user['membergroupids'] = $tempuser['membergroupids']; 
    $user['usergroupid'] = $tempuser['usergroupid']; 
    //$user['membergroupids'] .= ','.$tempuser['usergroupid']; 
} 
//else 
//{ 
//    $user['membergroupids'] .= ','.$user['usergroupid']; 
//} 


//if (in_array(24,explode(',',$user['membergroupids']))) 
if (is_member_of($user, 24)) 
{

but I'm not sure that fixes everything. I noticed "rainbow" didn't seem to work, and I don't know why the problems only happened with non-admin or mod users.