Alsamixer - Muting Master or Surround channel mutes both of them

Binary package hint: gnome-alsamixer

Hello!
I've just upgraded my Ubuntu 9.04 to 10.04.
I've noticed a bug (i guess) that wasn't there 2 versions ago (i'm sure):
When i try to mute either Master or Surround, both of them are muted, but if i only change their volume value, it does it only on the channel i modified.

I'm using it because i've a 5.1 sound card, and a 3.1 audio system. I plug my headphone (used with skype) in the last stereo channel (the one named Surround).
Until now, using 2 scripts, i used to switch the sound "off" for Master and "on" for Surround, to take a private call, and then "on" for Master and "off" for surround after the call (or to make a public call).

It used to work. It does not anymore with the new version.
Here is one of the scripts :
   amixer set "Front" unmute
   amixer set "Surround" mute
I guess you could imagine the other script...

From now, i will use "100%" instead of "unmute" and "0%" for "mute", but as i think that's a bug, i wanted to tell it. With this bug, the program won't remember the previous volume for the chanel, and i'll have to put it to 100%, instead of letting it to its original value.

Thank you having read my long poor english's bug report, and for the work you're doing!