Sometimes when I insert an audio CD I get a dialog that says "You have
just inserted an Audio CD. Choose what application to launch." It
doesn't show up for every CD... probably something like once for every 5
CD insertions.

Every single time I select "Do Nothing" and ensure that the "Always
perform this action" checkbox is checked. I assume the point of the
checkbox is to let me make the decision once and for all, but this
dialog continues to reappear periodically. Now when the dialog appears
"Do Nothing" is selected and "Always perform this action" is already
checked!

Work around:

I asked about this on askubuntu.com. It was suggested that I should got
to the Media tab in Nautilus's preferences and set the "Do Nothing"
option there. I went to do that and found that "Do Nothing" was already
set. I just dismissed the preferences dialog, but since then the problem
has not reoccurred. It's pretty weird that opening and closing a
settings dialog without adjusting any of the settings would have any
sort of lasting effect...

Other details that may or may not be of use to you:

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: nautilus 1:2.30.1-0ubuntu1.1
ProcVersionSignature: Ubuntu 2.6.32-24.43-generic-pae 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic-pae i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Fri Oct 22 12:02:12 2010
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: nautilus