Plugin admin settings not saving in network admin level only

add_action( 'admin_menu', array( &$this, '_settings_menu' ) );
add_action( 'network_admin_menu', array( &$this, '_settings_menu' ) );

I’m using [admin_menu] and [network_admin_menuu] actions to create some option pages for my plugin and the saving operations working great in both WordPress Single & Multisite blogs.

BUT, In the network admin level [ /wp-admin/network/admin.php?page=plugin_settings ] NOT [ /blog-1/wp-admin/admin.php?page=plugin_settings ]

After saving the page redirect to [ /wp-admin/network/options.php ] and the following error appears and of course won’t save the test values.

Object not found! The requested URL was not found on this server. The link on the referring page seems to be wrong or outdated. Please inform the author of that page about the error. If you think this is a server error, please contact the webmaster.

Note: The plugin is Activated under Network