Changing Original Size breaks entire module

Going to admin/settings/image and changing Original size to say just a width of 100 and leaving height breaks the entire module - ie when I try to attach an image to a node after making this change, after hitting the submit button I am left with a blank page. I had to reinstall the entire module again and lost all my images in my nodes! I leave these width and height field blank now and it seems to work. Perhaps it's because I have an improper install of image magick ??

(I upgraded because I changed the width and height on my 5.x-1.4 and it sent sendmail into a loop sending off 1000 emails!!)