Comment 2 for bug 891424

I can confirm the same behavior with Linux Mint 12 x64.

Hardware volume keys work correctly in Gnome Shell.

In Keyboard Shortcuts, I have:

Volume mute: XF86AudioMute
Volume down: XF86AudioLowerVolume
Volume up: XF86AudioRaiseVolume

I have tried reassigning the Shortcut keys again, with no effect.

In Sound Preferences I have:

Device HDA Intel (Alsa mixer)

In Configuration Editor, there is nothing set for default_mixer_device or default_mixer_tracks.

I tried setting default_mixer_device to alsamixer with no improvement.

I confirmed that the keypress is being sent by running:

xev | sed -n 's/^.*state \([0-9].*\), keycode *\([0-9]\+\) *\(.*\), .*$/keycode \2 = \3, state = \1/p'