FCP 7 ignores PNG transparency if you don't design the "right" way :)
All good until I export the thing. It took me 2 hours to understand why FCP 7 is ignoring png transparency. Apparently, it's not how you export it, it's not the content (weird layers modes), and it's not even the DPI setting. It is the design itself. For some reason, FCP thinks you should never attempt to bring in a lower third that starts at the bottom of the screen, filling it completely. So there ya go. If you want PNG transparency, DO NOT FILL THE BOTTOM PART OF THE IMAGE. Leave some transparent space. Talk about putting your creativity on a leash.
To better illustrate this odd behavior which I would classify as a bug, I wasted 5 minutes recreating my "problem" for the world to see.
Have fun!
http://vimeo.com/19856624
Mac Pro, Mac OS X (10.5.8)