just a thought.. maybe that one picture has a problem.. .. some error in it.. or in header
try to load it in photoshop.. and save as a different name and try again..
I would delete that one picture and try uploading or processing multiple files without using that one file and see how it goes most likely that one file is corrupt.
I think it's my pictures only. My pics are huge (3264X2448) and that's the problem. My other admin is uploading images like crazy and haven't heard any problems from him.
My host (Host Gator) said Imagemagick is installed too.