Guys if I tell you what happened to me you will laugh.
I had the same problem with media library,suddenly all images were lost.
I couldn’t put a simple image in a post and I couldn’t upload via wp-uploader.
All images and image uploading was disabled.
What happened? I opened my theme’s functions.php and I started debugging line by line.
I deleted everything that I had in functions.php and everything worked again!
The problem was that I had by accident two extra line spaces after the end of php tag “?>”
