I have the same problem on my laptop ACER 1705 trying to map the unrecognized media keys.
I tried to map 2 keys to 'F21' and 'F22' using xmodmap.
This works ok and 'xev' confirm that.
Then I am able to map those keys in 'Preferences/Keyoard_Shortcuts' or in compiz 'ccsm'.
Everything works until I restart X or reboot.
(I tried running the xmodmap association script in the session startup; in gdm/Init; in gdm/Postlogin; in gdm/Presession)
After X_restart or reboot, the keys are still correctly recognised by 'xev' but the shortcut associations do not work anymore.
Looking in 'Preferences/Keyoard_Shortcuts' the mapping is still there, but it seems to be ignored.
I have to disable the mapping,then set it back to 'F21' manually. After that, the shortcut works again.
I have the same problem on my laptop ACER 1705 trying to map the unrecognized media keys.
I tried to map 2 keys to 'F21' and 'F22' using xmodmap.
This works ok and 'xev' confirm that.
Then I am able to map those keys in 'Preferences/ Keyoard_ Shortcuts' or in compiz 'ccsm'.
Everything works until I restart X or reboot.
(I tried running the xmodmap association script in the session startup; in gdm/Init; in gdm/Postlogin; in gdm/Presession)
After X_restart or reboot, the keys are still correctly recognised by 'xev' but the shortcut associations do not work anymore.
Looking in 'Preferences/ Keyoard_ Shortcuts' the mapping is still there, but it seems to be ignored.
I have to disable the mapping,then set it back to 'F21' manually. After that, the shortcut works again.
This bug might be related to Bug #289781.