I know of two other options for Flash support under FF on Linux, but both are worse than Adobe's plugin, in my experience:

 * gnash:  Youtube video and sound work.  Many other flash sites fail.
 * swfdec:  Youtube video works, but I get no audio.  Many other flash sites fail.

I think the problem is that neither gnash nor swfdec support Flash 10 features--I don't know whether 10 represents a new file format, or just some extensions.  When the Adobe plugin is installed, FF's about:plugins page lists both Shockwave 9 and Shockwave 10 support, while it only shows 9 with gnash/swfdec.

If you want to try them, do a 'yum remove flash-plugin' and then do (for gnash) `yum install gnash gnash-plugin`, or (for swfdec) do `yum install swfdec swfdec-gtk swfdec-mozilla gstreamer-ffmpeg`.  I don't know what happens when both are installed at once, you could certainly try it.  Make sure to restart FF after installing a new plugin, too.

I'm running F11 x86-64, so it's a little different from your setup.  Maybe you will get better results than I did.  Good luck.

-Ryan