icons for custom mime-types on ubuntu 8.04

[Michael Brewer-Davis <michael tech4learning com>]

First, apologies if this is misdirected.  I know my issue touches a lot 
of packages (nautilus, ubuntu, xdg-mime, my own...).

My application installs new mime types and icons using xdg-utils.

On Ubuntu 8.04, nautilus (2.22.2-0ubuntu4) does not use the custom icon. 
 It does display the custom mime type (View as List/Type, Properties). 
 The system file dialog (used by Firefox, gedit, gimp) *does* use the 
custom icon.

On Ubuntu 7.10 and OpenSUSE 10.3, mime types and icons both work as 
expected with similar post-install environments.

Is this a bug or is there something wrong with my installation process? 
 Has something changed in the icon retrieval process?

Details follow--feel free to ask for more.  I appreciate any help, 
redirection, or general goodwill.

Thanks,
michael


Problem system:
Ubuntu 8.04; nautilus 2.22.2-0ubuntu4; xdg-utils 1.0.2-2

Okay systems:
Ubuntu 7.10; nautilus 2.20.0-0ubuntu7; xdg-utils 1.0.1
OpenSUSE 10.3; nautilus 2.20.0-5.2; xdg-utils 1.0.1

My installed files:
/usr/local/share/icons/hicolor/48x48/mimetypes/application-mymime.png
/usr/local/share/icons/hicolor/48x48/mimetypes/gnome-mime-application-mymime.png
 (softlink)
/usr/local/share/mime/application/mymime.xml

(the Ubuntu 7.04 machine has some KDE components installed, so xdg-utils 
also put icons in the /usr/share/mimelnk directory)

My mime installation process:
sudo xdg-mime install --mode system my-mime.xml

my-mime.xml:
<mime-info xmlns="...">
  <mime-type type="application/mymime">
    <comment>My MIME file</comment>
    <glob pattern="*.mzm" />
  </mime-type>
</mime-info>

sudo xdg-icon-resource install --context mimetypes --size 48 --mode 
system iconfile.png application-my-mime

iconfile.png is a 48x48 PNG