Gnome shell missing some icons after upgrade

[Andy Campbell]

Hi All,

I just completed an upgrade of my system from FC16 32bit to FC16 64bit.
During the upgrade I reformatted all disks, except for the /home mount.
I retained /home so all my personal settings were retained correctly.  

Everything seems to have worked great, except that gnome-shell is
missing some application icons in the start menu.  Check out the screen
shot here
http://dl.dropbox.com/u/3289905/missing.icons.png

You can see that Ardour, Calf, Ffado, Hydrogen etc have broken icons.
There are a few items scattered across all the menus like this.  It
looks like all of these are apps which I installed after completing the
base install using yum.

Changing the icon theme does not seem to make a difference - it looks
like the same icons are missing in all themes.

I can see that there are icons for these apps:
[andy at speedy]# find /usr/share/icons/ -name ardour*
/usr/share/icons/hicolor/48x48/apps/ardour2.png
/usr/share/icons/hicolor/32x32/apps/ardour2.png
/usr/share/icons/hicolor/22x22/apps/ardour2.png
/usr/share/icons/hicolor/16x16/apps/ardour2.png
/usr/share/icons/gnome-colors-common/32x32/apps/ardour.png
/usr/share/icons/gnome-colors-common/scalable/apps/ardour.svg
/usr/share/icons/gnome-colors-common/24x24/apps/ardour.png
/usr/share/icons/gnome-colors-common/22x22/apps/ardour.png
/usr/share/icons/gnome-colors-common/16x16/apps/ardour.png

I can also see that one of my icon themes (fedora-icon-theme) has an
fc15 version of the rpm (but I cannot find an fc16 version)
[andy at speedy icons]# rpm -qa | grep icon-theme
gnome-icon-theme-symbolic-3.2.1-1.fc16.noarch
gnome-icon-theme-legacy-3.2.1.2-1.fc16.noarch
gnome-icon-theme-extras-3.0.0-2.fc16.noarch
fedora-icon-theme-1.0.0-11.fc15.noarch
gnome-icon-theme-3.2.1.2-1.fc16.noarch
gnome-colors-icon-theme-5.5.1-2.fc15.noarch
hicolor-icon-theme-0.12-3.fc16.noarch

Is there a cache or a setting somewhere in my home folder which could
break icons after an upgrade from 32 bits to 64 bits?

Does anybody have any advice on how to troubleshoot this?

Thanks

Andy