$usr->getRight() works with MDB2 but not with DB

Hello list,

strange things happens...
for testing i have

- two rights:
			right_id  area_id  right_define_name  has_implied
  			1 		1 		Operator 		N
  			2 		1 		Admin 		N

- two auth-/perm-users: '7123' with perm_user_id = 1 and 'admin' with
perm_user_id = 2

- two groups: 'operator' with group_id = 1 and 'admin' with group_id = 100

- groupusers: perm_user_id	group_id
			1			1
			2			100

- two grouprights:
 		group_id  	right_id  	right_level
  			1 		1 		1
			100 		2 		3

Means (should): user "Admin" is in group "Admin" and has right "Admin", user
"7123" is in group "Operator" and has right "Operator".

$usr->getRight('Admin') returns the right_level (3) if i use MDB2. If i
change the same config to use DB instead of MDB2 it returns false

I'm using the latest pear-versions of all packages (no cvs)

My config (is just from one example):

require_once 'MDB2.php';
//require_once 'DB.php';
require_once 'LiveUser.php';
// Plase configure the following file according to your environment

$dsn = 'mysql://user:pass@host/liveuser';

$db = MDB2::connect($dsn);
//$db = DB::connect($dsn);

if (PEAR::isError($db)) {
    echo $db->getMessage() . ' ' . $db->getUserInfo();
}

//$db->setFetchMode(DB_FETCHMODE_ASSOC);
$db->setFetchMode(MDB2_FETCHMODE_ASSOC);

$conf =
    array(
        'autoInit' => false,
        'session'  => array(
            'name'     => 'PHPSESSION',
            'varname'  => 'ludata'
        ),
        'login' => array(
            'force'    => false,
        ),
        'logout' => array(
            'destroy'  => true,
        ),
        'authContainers' => array(
            'DB' => array(
                'type'          => 'MDB2', //DB
                'loginTimeout'  => 0,
                'expireTime'    => 3600,
                'idleTime'      => 1800,
                'allowDuplicateHandles' => 0,
                'storage' => array(
                    'dsn' => $dsn,
                    'alias' => array(
                        'lastlogin' => 'lastlogin',
                        'is_active' => 'is_active',
                    ),
                    'fields' => array(
                        'lastlogin' => 'timestamp',
                        'is_active' => 'boolean',
                    ),
                    'tables' => array(
                        'users' => array(
                            'fields' => array(
                                'lastlogin' => false,
                                'is_active' => false,
                            ),
                        ),
                    ),
                )
            )
        ),
    'permContainer' => array(
        'type' => 'Medium',
        'storage' => array('MDB2' => array('dsn' => $dsn, 'prefix' =>
'liveuser_')),
	//'storage' => array('DB' => array('dsn' => $dsn, 'prefix' =>
'liveuser_')),
    ),
);

PEAR::setErrorHandling(PEAR_ERROR_RETURN);

$usr = LiveUser::singleton($conf);

$handle = (isset($_REQUEST['handle'])) ? $_REQUEST['handle'] : null;
$passwd = (isset($_REQUEST['passwd'])) ? $_REQUEST['passwd'] : null;
$logout = (isset($_REQUEST['logout'])) ? $_REQUEST['logout'] : false;
$remember = (isset($_REQUEST['rememberMe'])) ? $_REQUEST['rememberMe'] :
false;

if (!$usr->init($handle, $passwd, $logout, $remember)) {
    var_dump($usr->getErrors());
    die();
}

May be that I've done some mistakes, but it looks more like a bug(?)

Regards
Jens