Media library doesn't load images (WordPress)

Error
  • Media library, from where you can upload and select your images doesn't load the images, only a failed loading screen appear.
  • In Firefox the error message is: Content Encoding Error.
Solution

This error can happen because of Headway theme. If you have that theme, go to the WordPress' left admin menu Headway → Options → Advanced, and turn the gzip Compression off. If you don't have this theme, you can try to disable your other plugins, and if that doesn't help the error will be with your theme, and you can confirm it by changing it. You can google the error message with your theme's name, and you might find a solution, or try to contact the theme developers.

Another issue could be, that a server limitation is reached, like the memory_limit.

Known plugins and themes where the problem occurred:
  • Headway theme
  • Etsy360 plugins (disable the plugins and contact the developer for a solution)