convert zca-8.0.0.0.ova to kvm

Hi

I like to run the zca 8 ova under kvm.

I tried to convert the vmdk files to qcow2.

o tar xfv ../zca-8.0.0.0-1147_OVF10.ova
o qemu-img convert -O qcow2 zca-8.0.0.0-1147-data.vmdk zca-8.0.0.0-1147-data.qcow2

--> error : qemu-img: error while reading sector 458752: Invalid argument

any ideas?

cheers