The issue is that one or more images were uploaded which are too large for WP to process to create thumbnails.
Using FTP, navigate to this folder:
You will find a folder for each entry. Within that folder you will find the original image uploaded for the entry. Download that image, scale it down and then upload it again overwriting the image that was downloaded.
After you do that, the page will load fine.
Hope that helps, let me know.