Custom background not loading for Headline Animator

[Eric]

Greetings - I can't seem to create a gif that Headline Animator likes for a background. I see the background load successfully at the bottom of the setup screen where I'm able to layout the text, but the "final", processed image shows up as a broken image both at the top of the setup page and anywhere I try to render the image directly.

I've seen others post about this. Are there some special GIF output settings needed to make this work? Photoshop and Pixelmator, both on the Mac, have failed to work correctly. My images are 320x75, above the 21 pixel limit bug reported back in '07.