Quite a lot of people meet the issue like 'HTTP error 0 occurred' in Drupal when they work with large file or image. And unfortunately, today I meet the same issue today. After some investigation, the issue is gone after increase "memory_limit" in php.ini.

"memory_limit" is directive of maximum amount of memory a php script may consume. The default value in php.ini is 64M in my case. For my Drupal site, I have enabled ImageCache module, when I upload an image with 2M, system will need around 128MB to scale the image to what I need. This is the major reason it's failed. As some of my image go to 4MB, I decide to increase my "memory_limit" to 256MB.

Hopeful, this is helpful for you.