I get a lot of broken images. Almost every image that needs resized, comes out broken. It does so after about 2s of processing something. And then the next one (fails too), and the next, and the next, and so on.
On my server, I can clearly see the apache2 processing sweating like a horse to (presumably) resize those images. So it's doing something, but what?
At the time of writing, my server has over 2.5GB of completely unused memory. Also it has enough horsepowers, and plenty of free disk space. It's also set up to use imagemagick.
PHP related config:
max_execution_time 120
max_input_time 120
memory_limit 500M
Server details:
Apache 2.4.18
PHP 5.6.18
MySQL 5.5.47
ImageMagick 6.7.7-10
Zenphoto 1.4.9