Xen pci passthrough: PCI Backend and pci-stub don't own sibling device 0000:00:00.0

When starting a xen virtual machine with pci-passthrough of my pci cards, it complains about xen pciback not owning the device 0000:00:00.0, but it is not supposed to own that device (since it is the pci root).
I found someone reporting this, and providing a workaround (probably not a real solution) in the following mailinglist post(s):

Problem:
http://osdir.com/ml/xen-users/2011-04/msg00207.html

Workaround:
http://osdir.com/ml/xen-users/2011-04/msg00210.html

Note: I'm running ubuntu 12.04, and have done a update & upgrade today.

root@hoth:/usr/lib/xen-4.1/lib/python/xen/xend/server# apt-cache policy xen-tools xen-utils-4.1 xen-hypervisor-4.1-i386
xen-tools:
  Installed: (none)
  Candidate: 4.2.1-1
  Version table:
     4.2.1-1 0
        500 http://nl.archive.ubuntu.com/ubuntu/ precise/universe amd64 Packages
xen-utils-4.1:
  Installed: 4.1.2-2ubuntu1
  Candidate: 4.1.2-2ubuntu1
  Version table:
 *** 4.1.2-2ubuntu1 0
        500 http://nl.archive.ubuntu.com/ubuntu/ precise/universe amd64 Packages
        100 /var/lib/dpkg/status
xen-hypervisor-4.1-i386:i386:
  Installed: (none)
  Candidate: 4.1.2-2ubuntu1
  Version table:
     4.1.2-2ubuntu1 0
        500 http://nl.archive.ubuntu.com/ubuntu/ precise/universe i386 Packages

root@hoth:/usr/lib/xen-4.1/lib/python/xen/xend/server# apt-cache policy linux-image
linux-image:
  Installed: (none)
  Candidate: 3.2.0.17.17
  Version table:
     3.2.0.17.17 0
        500 http://nl.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages