Comment 1 for bug 377175

I'm having the same problem. Ubuntu 9.04 with a Macally Icekey USB keyboard. This is new after upgrading from 8.04 -> 8.10 -> 9.04 last night. I've tried both the Generic keyboard layout (pc104 and pc105), as well as evdev-managed keyboard. I figured out the following:

1. In Jaunty, keycode 160 is my volume up key
2. It's original mapping was XF86ScreenSaver
3. I can change it: xmodmap -e "keycode 160 = XF86AudioRaiseVolume"
4. Then I end up in the same spot as Matt -- pressing the key causes the volume to go up AND locks the screen.

It seems like something in Gnome has attached to the XF86ScreenSaver key, and when the keysym for keycode 160 changed, it didn't update internally. Digging through all the configuration in gconf-editor, it doesn't appear that the screensaver key behavior is configurable.

(The "lock screen" keyboard shortcut is still set to the original value, <Ctrl><Alt>L. Changing or disabling that doesn't stop this from happening.)

My other three "special" keys, lower volume, mute, and eject, all work fine.