ok i have fixed it by change in the arcade_play.php (seen trick in page 3 of this post) :
thank you Ango for this and this fabulous mod. Tell me if it is an error to do this modification like this.
found :
$line = $db->fetch_assoc($result);
if ($line['game_id'] <= 0)
message($lang_common['Bad request']);
replaced by :
if(mysql_num_rows($result) <= 0)
message($lang_common['Bad request']);
$line = $db->fetch_assoc($result);
all is working !!:D