White Screen on Plugin Settings adter Smush Pro Install

Hi, I love your plugin. I installed the free version and it was working properly. then i deleted it and uploaded the Wp Smush Pro. When I open http://www.stylondo.com/wp-admin/upload.php?page=wp-smush-bulk I do see a grey screen only.

I am running the latest versio of Wordpress on an Amazon EC2 instance. I also have Amazon CloudFront installed and new images are saved on Amazon S3.

Any ideas?

Best,
Thomas