It may be the GD Library is not enabled on the host server.
If you send a link where i can see the problem to investigate, i'll be able to tell if that is the case.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.