Ok, Nikos. I tried uploading two photos (jpg) and received an error message for both. The file size is under the limit, so what else could it be?
Error creating thumbnail! Error code: 127
Command:
"/usr/X11R6/bin/mogrify" -size 100x75 -quality 70 -geometry 100x75 '/home/longhair/public_html/gallery/data/500/2152051404_1056-thumb.jpg'