If you have installed Leopard and want to be able to upload files but at the same time debug your Flash and Flex applications you can find the debug versions of the prerelease player (that has the file upload fix) in the Flex 3 SDK nightly builds, just download, unzip and look in the “runtime” directory.
This wasn’t obvious to me, and I spent a long time hunting it down. I hope this comes to use the next time someone googles for leopard debug flash player.
Edit Since 10.5.1 came out, this became a little less useful. Go with the release version for development instead of using the nightlies.
Edit This page http://www.adobe.com/support/flashplayer/downloads.html lists the latest version of the release debug player.