open lib/engine.php like 76 (protected $mime_types) and delete that types,

change it from

    protected $mime_types = array(

        'video' => array(
            'video/mp4' => 'mp4',
            'video/m4v' => 'm4v',
            'video/mov' => 'mov',
            'video/wmv' => 'wmv',
            'video/flv|video/x-flv' => 'flv',
        ),

        'audio' => array(
            'audio/wma' => 'wma',
            'audio/m4a' => 'm4a',
            'audio/mp3' => 'mp3',
            'audio/wav' => 'wav',
            'audio/mpeg' => 'mpeg',
            'audio/flv|audio/x-flv' => 'flv',
        ),

        'image' => array(
            'image/gif' => 'gif',
            'image/jpeg' => 'jpeg',
            'image/jpg' => 'jpg',
            'image/png' => 'png',
            'image/x-ms-bmp' => 'bmp',
        ),

        'flash' => array(
            'application/x-shockwave-flash' => 'swf',
        ),

        'compressed' => array(
            'application/x-bzip' => 'bz',
            'application/x-bzip2' => 'bz2',
            'application/zip' => 'zip',
            'application/x-rar-compressed' => 'rar',
        ),

        'text' => array(
            'application/x-sql' => 'sql',
            'text/plain' => 'txt',
        ),

    );

to

    protected $mime_types = array(

        'video' => array(
            'video/mp4' => 'mp4',
            'video/m4v' => 'm4v',
            'video/mov' => 'mov',
            'video/wmv' => 'wmv',
            'video/flv|video/x-flv' => 'flv',
        ),

        'audio' => array(
            'audio/wma' => 'wma',
            'audio/m4a' => 'm4a',
            'audio/mp3' => 'mp3',
            'audio/wav' => 'wav',
            'audio/mpeg' => 'mpeg',
            'audio/flv|audio/x-flv' => 'flv',
        ),

        'image' => array(
            'image/gif' => 'gif',
            'image/jpeg' => 'jpeg',
            'image/jpg' => 'jpg',
            'image/png' => 'png',
            'image/x-ms-bmp' => 'bmp',
        ),


        'compressed' => array(
            'application/x-bzip' => 'bz',
            'application/x-bzip2' => 'bz2',
            'application/zip' => 'zip',
            'application/x-rar-compressed' => 'rar',
        ),



    );