This may seem extremely trivial for many people out there.. but all it takes is a forgetful server admin.
I had an old box that needed reloading, so I had to reinstall the GD library for php using YUM.
# yum install php-gd
Is all it takes to install gd for php. I’ve forgotten the php- part so I’ve tried installing gd-devel, gd-progs and other crap I didn’t need… it’s so simple sometimes.