widgets.php is returning 404 Error after 3.4 WP update

Hi there,

After updating WordPress to the 3.4.1, Widget Visibility started causing widgets.php page to return 404 error.

It works just after I deactivate the plugin. When I activate it again, widgets.php returns 404 error again.

Please can you help?

Thanks

https://ww.wp.xz.cn/plugins/widget-visibility/