When uploading large images over an approximate size (~2500×2000) I was encountering the HTTP Error message when trying to crunch the image (which ultimately fails and doesn’t produce the smaller pre-defined image sizes).
After trying several solutions, the following appears to have solved it for my setup, once and for all – add this to your .htaccess file:
In short, it massively bumps up the allowed memory limit, and also tries to turn off some security aspects for the file that deals with the uploading, under different module setups.
REALLY WORKING – THANK YOU!!!