Mixer unit "software" doesn't work after upgrade

Under Settings > Generel > Sound mixer I can choose "software" as my mixer unit.

In Ubuntu 10.04, 10.10 and 11.04 I was no able to control or mute the sound with the volume keys on my keyboard/remote control.

However in the upcoming version of Mythbuntu 11.10 if I press the volume keys nothing happens.
If I go outside Mythtv I've problems adjusting the volume with the volume keys on my keyboard.

My box is an Asorck Nettop 330HT-BD with the Nvidia ION-chip using the proprietary Nvidia-driver connected to a LG HD-ready TV (LG 32LC56) though a HDMI cable.

If I chosen "ALSA:defalut" as my Mixer unit in the earlier releases I would still be able to use the volume keys on my keyboard and remote control but they wouldn't have any effect.