Hello.
I think that the problem is related somehow with communication between XP
and PDC, because if I enable Netbios over TCP/IP it works sometimes.
Anyway, as a workaround, I coded this simple script that works. Maybe you
find it useful:

code:
Function belongsToGroup($username, $groupname)

    If @INWIN<>2 ;Windows 2000/XP
            $domain = GetObject("WinNT://@LDOMAIN")
            $domain.filter = "group",""
            
            $belongsToGroup = 0

            For Each $group in $domain 
                If $group.name = $groupname
                    For Each $user in $group.members   
                          If $user.name = $username
                              $belongsToGroup=1
                           EndIf
                    Next
                EndIf
            Next
    Else ;Windows 9x
        $belongsToGroup = InGroup($groupname);
    EndIf
EndFunction