Graph API: Unknown error getting fql multiquries

I have a problem with the PHP SDK:

$fql="{'query1':'SELECT uid2 FROM friend WHERE uid1=me()',
         'query2':'SELECT author_uid FROM checkin WHERE author_uid IN(SELECT uid2 FROM #query1) AND page_id = $page_id'}";

     $friends= $facebook->api(array(
       'method' => 'fql.multiquery',
       'queries' => $fql,
      'access_token' => $access_token
     ));

And I use a lot of page identifiers.

When I ran this script in https://graph.facebook.com/fql/?access_token=AC&q=QUERIES it works fine.

But when I use php-sdk, sometimes it works, but for some pages it returns me an error:

FacebookApiException Object
(
    [result:protected] => Array
        (
            [error_code] => 1
            [error_msg] => An unknown error occurred
        )

    [message:protected] => An unknown error occurred
    [string:Exception:private] => 
    [code:protected] => 1
    [file:protected] => /APP_PATH/base_facebook.php
    [line:protected] => 1249
    [trace:Exception:private] => Array
        (
            [0] => Array
                (
                    [file] => /APP_PATH/base_facebook.php
                    [line] => 816
                    [function] => throwAPIException
                    [class] => BaseFacebook
                    [type] => ->
                    [args] => Array
                        (
                            [0] => Array
                                (
                                    [error_code] => 1
                                    [error_msg] => An unknown error occurred
                                )

                        )

                )

Can anybody help me? I can’t understand why I get this error .....