Well you wiped out my name and your server does not send email again. I did not get a blank page. I got the actual php file downloaded to my desktop meaning PHP was shutting down on the folder when I tried an upload
Since your PHP is so old all I can do is suggest the changes noted. Your Imagemagick is also very old. I guess seeing a situation as this your host is not going to help here.
My suggestion would be to upgrade PHP ImageMagick and reset permissions on the Photopost per the install manual here especially the uploads and data directory permission http://www.photopost.com/installphp.html