virt-manager system tray menu is missing icons

[Alvin]

- Edit > Preferences > General > Enable system tray icon
- Right-click on the system tray icon
   The icon for 'Quit' is missing
   Icons for the host and its 'Play', 'Pause' and 'Open' buttons are missing.

No icons are missing from the Virtual Machine Manager window itself. (gnome-icon-theme is installed)

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: virt-manager 0.9.5-1ubuntu3
ProcVersionSignature: Ubuntu 3.13.0-30.54-generic 3.13.11.2
Uname: Linux 3.13.0-30-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: KDE
Date: Thu Jul 3 14:39:54 2014
InstallationDate: Installed on 2014-06-28 (4 days ago)
InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
PackageArchitecture: all
SourcePackage: virt-manager
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Alroger Filho (alroger-filho)]

Greetings.

I started to notice this since Ubuntu 10.04 LTS, and still see this simptom on 15.04 now.
I've never figured out why, but it started on a server update with 10.04... it left my office working, through ssh -X, our -YC and after a few months updates stopped showing the icons.

I just formatted a new Xubuntu 15.04 64bits on my desktop+server, copied a few /etc configs, KVM folders, etc.... It looked fine on Xubuntu 14.04, 14.10 and Sparky. And now I don't have the icon.

I thought it was a remote ssh problem, that I still see in a few customers. But now my machine presents it.
I have just tried a live Xubuntu 15.04 64bits on a VM, installed virt-manager only, and the icons work.

All that brings the question: what could be updated or installed that would mess up those icons? The package should have it's own default fallback icons, shouldn't it?

A couple pics attached.