Same problem here. Using a Macally Icekey keyboard
The Volume up key on this keyboard produces "keycode 160 (keysym 0x1008ff2d, XF86ScreenSaver)" using xev. And it seems this "XF86ScreenSaver" is hard coded somewhere in X or gnome so you can't reallocate it using the usual gnome keyboard shortcuts program.
In my case though I've disabled gnome-screensaver, to use xscreensaver. So this key does nothing. And I also can't reallocate it to something else useful, like putting the volume up!
Same problem here. Using a Macally Icekey keyboard
The Volume up key on this keyboard produces "keycode 160 (keysym 0x1008ff2d, XF86ScreenSaver)" using xev. And it seems this "XF86ScreenSaver" is hard coded somewhere in X or gnome so you can't reallocate it using the usual gnome keyboard shortcuts program.
In my case though I've disabled gnome-screensaver, to use xscreensaver. So this key does nothing. And I also can't reallocate it to something else useful, like putting the volume up!