Your files (ezMedia?) worked fine. I'm still getting odd behavior on some, not all, of mine.
http://homepage.mac.com/kkirkster/3woodencrosses/index.html
1.3MB's. It loads "full screen" but notice what happens when you change the size (Command - 0, 1, 2 or 3). The green color is my "transparent color".
Hit the "Escape" key to bring it out of full screen mode and adjust the size again. The "mask" is revealed and doesn't revert. A pixel "shift" in the mask track when changing size (notice the green line next to the text box)
I can't be sure if I tested in this fashion prior to 7.0.4.
Odd.