Why I can't control volume with volume button

Hi,

I'm using xmms-1.2.10-2.2.p.1.fc2.fr in Fedora 2 to play music ( I use
Labtec USB Headset as audio device) . I found 1 problem there: Only the
first user who use graphic login can control the audio volume while drag
the volume button on Xmms interface. Other user can't use control volume
even I modify permission of  /dev/snd/* to 666. Here is a detail test
process:

1) Use "testuser1" to login in graphic interface of Fedora 2; After log
in, I can see all the device in /dev/snd/* change owner to
testuser1:root. The permission is 700. And I play audio with Xmms,
config xmms to use ALSA output plugin, select "Audio device" to
"hw:0,0", click "Use software volume control",  I can use volume button
to control volume while playing audio file.

2) Change permission of /dev/snd/* to 666. And use "su - testuser2" to
enter testuser2. I launch xmms with "xmms" command line here. Same
config as above in 1). But I can't control volume now. And the output
error is as followed:

"** WARNING **: alsa_setup_mixer(): Failed to find mixer element: PCM"


Anyone can give me an idea about it? I'd like to make volume work for
all the users.


Thanks.


Rocky