Comment 6 for bug 281732

I can confirm this bug on up-to-date Kubuntu Jaunty on ThinkPad x200s.

Pressing Mute button does not generate HAL event (lshal -m) and does not issue KeyPress X event (xev). I can confirm that pressing Mute button changes state reported by /proc/acpi/ibm/volume:

Before:
level: 7
mute: off
commands: up, down, mute
commands: level <level> (<level> is 0-15)

After:
level: 7
mute: on
commands: up, down, mute
commands: level <level> (<level> is 0-15)

Volume Up/Down keys work properly and generate both HAL and X event:

lshal -m
=====

Start monitoring devicelist:
-------------------------------------------------
10:25:04.550: platform_i8042_i8042_KBD_port_logicaldev_input condition ButtonPressed = volume-up
10:25:05.323: platform_i8042_i8042_KBD_port_logicaldev_input condition ButtonPressed = volume-down

xev:
===
FocusIn event, serial 31, synthetic NO, window 0x3400001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 31, synthetic NO, window 0x0,
    keys: 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

KeyRelease event, serial 31, synthetic NO, window 0x3400001,
    root 0xb4, subw 0x0, time 8684461, (66,77), root:(1119,215),
    state 0x0, keycode 123 (keysym 0x1008ff13, XF86AudioRaiseVolume), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

FocusOut event, serial 34, synthetic NO, window 0x3400001,
    mode NotifyGrab, detail NotifyAncestor

FocusOut event, serial 34, synthetic NO, window 0x3400001,
    mode NotifyUngrab, detail NotifyPointer

FocusIn event, serial 34, synthetic NO, window 0x3400001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 34, synthetic NO, window 0x0,
    keys: 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

KeyRelease event, serial 34, synthetic NO, window 0x3400001,
    root 0xb4, subw 0x0, time 8685027, (66,77), root:(1119,215),
    state 0x0, keycode 122 (keysym 0x1008ff11, XF86AudioLowerVolume), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

I am not sure hal-info is the right package for this - I think most of special keys are now handled in kernel.