I'm having great difficulty getting the Macromedia Flash Plugin to work, either in Mozilla or my favorite browser, Mozilla Firebird (which I installed with no problem to /usr/local/MozillaFirebird, with a link to /usr/local/firebird).
There is a discussion of this on LinuxQuestions.org. The solution seems to be resetting some of the soft library links that the fedora libstdc++ and compat-libstdc++ rpms set up. I'm not sure that I'm ready to do that, yet.
BTW, the main reason to have Flash installed is so that you can watch the new animated Doctor Who adventure from the BBC.