Comment 10 for bug 470636

If you're going with option 2., you can simply add the following line to /etc/apparmor.d/abstractions/libvirt-qemu file's end (after the HOME stuff)

/path/to/images_dir/** rw,

Then you can place you images for every guest in that folder or subfolders. Tested and working on Karmic.

Note that this is not as secure as option 1., but it is a quick fix if you're say on a private machine where only you have access to guests and you're doing a lot of guest creation/destroyingand you don't want to edit the profile for every one of them by hand.