Weird one, this. Running FC8 on an x86_64. The gnome-appearance-properties window doesn't function properly. It opens on the Themes tab OK and I can change themes. If I select the Background tab, that work too, though the thumbnails don't appear until I click in the window or on the scroll bar. The Fonts and Interface tabs don't respond at all if I click on them, though I can get them up from a terminal command line with the -p option. And after selecting Background I can't then get back to Theme. It also seems to hog the cpu too when it's running. Some of the screen buttons work, like Close, but not Help. And I can close the app from the title bar.
I've tried removing the gtk-qt engine (as suggested by some Ubuntu forums) and cleaning out old themes from /usr/share/themes which some posts suggested might cause the problem. I've also removed and r-installed control-center (which provides the app) all with no effect.
Now I'm stumped. Any help greatly appreciated.'