Cannot get Flash working with Fedora 11

[Doctor Who]

When I visit a site with Flash, either the area containing Flash
animations does not work (like adobe.com) or with a video (like
YouTube) I get the video initally then it just changes to a gray box.
I'm not sure what's going on here.

I thought it might have to do with Desktop Effects being enabled, but
when I disable I get the same behavior.

I have the following installed:

firefox-3.5-1.fc11.i586
flash-plugin-10.0.22.87-release.i386
libflashsupport-000-0.5.svn20070904.i386

Any help with this is greatly appreciated.