For others looking for help with PNGs, here are some links:
http://www.sitepoint.com/blogs/2007/09/18/png8-the-clear-winner/
http://blogs.cozi.com/tech/2008/03/transparent-png.html
http://www.satzansatz.de/cssd/tmp/alphatransparency.html
http://www.hrunting.org/csstests/iealpha.html
All good info.
-dean