[CentOS-virt] ovf conversion

I try do use one of the images available from [1] These images comes in two flavors, one vmx, one ovf.

I do not know how to convert one of these to centos6-libvirt-kvm

virt-convert gives me an error

$ virt-convert -i ovf -o virt-image path_to_image.ovf ERROR Couldn't convert disks: Disk conversion failed with exit status 1: qemu-img: Could not open 'path_to_image.vmdk'

The vmdk does exist. It seems that qemu-img can not handle this vmdk format. I am also not sure if v2v could do it.

I think the essence of my post is the question Is it possible to use vmx or ovf images with kvm, possibly after converting them?

[1] http://info.puppetlabs.com/download-learning-puppet-VM.html