Image Thumbnail Generation Hanging
When generating thumbnails, it's locking the browser for a period of time then failing to create the image.
This may be caused by a DNS issue. When thumbnails are generated, the script downloads a copy of the image via your site url. Sometimes your own server may not be able to reach it's own domain name via DNS. To fix this edit the /etc/hosts file on the server. Add an entry similar to:
If that doesn't fix the issue, try with the public server IP.