have you looked at your photopost database with phpMyAdmin or something to verify the tables and such are there?
As for the path to mogrify, do tou have telnet or SSH access? You can easily verify the path yourself if you do by typing "locate mogrify" at the command prompt. A lot of times hosts will either install old versions of ImageMagick, or install it incorrectly, or just plain not know the real path of the executable.
