[edgy regression] volume up/down/mute keys no longer work on g4-based mac mini

The volume buttons on my (remote) keyboard no longer work properly in Edgy. I've got a g4-based Mac Mini, and I'm using its built-in PCM device. There is only one software volume control in gnome-volume-control and alsamixer, and it's named "PCM". Of course, using this control works perfectly.

The problem comes when I attempt to use the volume keys on my keyboard. What happens is that the mini on-screen control pops up, but the speaker icon has a red cancel icon on it. Presumably, it can't find the "Main" control channel? Anyway, that's the only effect I see when I press those buttons. The volume level itself doesn't change.

Here is the driver load info:
burner@flambe:~$ dmesg |grep -2 snd
[ 65.186289] eth1: Found BCM5221 PHY
[ 67.585395] eth1: Link is up at 100 Mbps, full-duplex.
[ 69.118887] snd-aoa-fabric-layout: found bus with layout 58
[ 69.118898] snd-aoa-fabric-layout: Using direct GPIOs
[ 69.270847] snd-aoa-fabric-layout: can use this codec
[ 69.546854] apm_emu: APM Emulation 0.5 initialized.
[ 70.050055] SCSI subsystem initialized
[ 70.064533] ieee1394: sbp2: Driver forced to serialize I/O (serialize_io=1)
[ 70.064543] ieee1394: sbp2: Try serialize_io=0 for better performance
[ 70.118986] snd-powermac no longer handles any machines with a layout-id property in the device-tree, use snd-aoa.
[ 70.477490] Adding 1508984k swap on /dev/disk/by-uuid/a0df8e2c-d9a6-4dc0-96ff-3fb7d05b7068. Priority:-1 extents:1 across:1508984k
[ 70.655102] EXT3 FS on hda3, internal journal

PS, I'm not sure if gnome-media's the right place at which to submit this bug, but hopefully this can be redirected if needed.