Your problem I believe is a transparent background. The transparency looks great on screen and in print preview (because of the white background). If you were to create a background layer of white and then save your image it should print fine.
Here is an example that'll work.
Hope that helps.
I have this PNG that looks great on the screen (even in print preview mode), but when it gets printed from within Mozilla, it has an ugly black background. However, printing it in IE works fine. I created it in GIMP.
Please help!
Jack L. Wolfgang II
Volunteer WebServant, First Christian Church-Tallahassee, FL & Tri-State Christian Fellowship