While uploading photographs to my new blog, I have been having a lot of difficulties. The files upload but then I get a http error during the crunching stage. Once uploaded the images cannot be sized, only put up at there original size.
I spent sometime looking at the WordPress help pages but eventually I found the answer here: Just adding the line
AddType x-mapp-php5 .php
to the top of my .htaccess file, fixed my load problems. This file is located in the folder you installed your WordPress to on you host server.