Changing the default alert sound breaks desktop sound theme

Steps to reproduce:

1) Open a terminal, dconf-editor, and the Sound Configuration window.
2) Navigate to org.gnome.desktop.sound in dconf-editor. The value for the key named "theme-name" should be "ubuntu"
3) In the terminal, run the command:
     /usr/bin/canberra-gtk-play --id="dialog-question"
     You will hear the expected "drum beat" question sound.
4) Click on "Bark" in the Sound Configuration window to change the alert sound.
     a) You will notice that the theme-name in dconf-editor has changed to "_custom"
5) In the terminal, run this command again:
     /usr/bin/canberra-gtk-play --id="dialog-question"
     You will hear no sound and see the message "Failed to play sound: File or data not found"
6) Change the alert sound back to "Default" in the Sound Configuration window.
     a) You will notice that the theme-name in dconf-editor has changed to "freedesktop"
7) In the terminal, run this command again:
     /usr/bin/canberra-gtk-play --id="dialog-question"
     You will hear no sound and see the message "Failed to play sound: File or data not found"

In order to get Ubuntu's sound theme back, you have to manually change the value of theme-name in dconf to "ubuntu".

Expected behavior:

1) When changing alert sound back to "Default," the value of "theme-name" in dconf should revert to "ubuntu", not "freedesktop".
2) When choosing an alert sound other than "Default", users will not reasonably expect that many of their other system sounds will disappear. Only the alert sound itself should change.

More ideally, the selection should be among entire sound *themes*, like the moblin theme which is available in the repos.
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ApportVersion: 1.23-0ubuntu3
Architecture: i386
DistroRelease: Ubuntu 11.10
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
NonfreeKernelModules: nvidia
Package: gnome-settings-daemon 3.2.0-0ubuntu5
PackageArchitecture: i386
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic-pae 3.0.4
Tags: oneiric running-unity
Uname: Linux 3.0.0-12-generic-pae i686
UpgradeStatus: Upgraded to oneiric on 2011-10-13 (17 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare