I have a serval performance, and recently upgraded from 8.04 to 8.10. I noticed that my quick-buttons on the laptop for mute and volume up/down no longer work. I get the gnome popup, showing sound up/down, and mute/unmute, but that isn't tied into the actual sound anymore.
I checked System > Preferences > Keyboard shortcuts, and they are still set for XF86AudioMute, etc. (screenshot attached)
I have installed / setup compiz, but I didn't see any sound features associated with that. I don't have a .Xmodmap being loaded, either.
And yes, I moved from XFCE to regl'r gnome. I like the scale effect with compiz.
Is there somewhere else I should check for what the XF86* shortcuts are hooked in to?