Creating generic virtual appliance based on RH7

We are aiming to create a generic virtual appliance based on RH7. I performed a minimal installation of RH7 in virtual box and exported to an OVA file. Then I imported the OVA into Xen, however the virtual machine fails to start as it cannot find any of the partitions (see screenshot attached).

Error reported is:
Warning: /dev/disk/by-uuid/XXXXXXXX does not exist

Existing dracut presents further details:
Warning: Not all disks have been found
Warning: You might want to regenerate your initramfs

One work around I found is to boot using the rescue option in grub, which boots successfully, and then to regenerate the initramfs using "dracut -vf"

After this step I am able to boot successully using the standard (non-resuce) option in grub.

Is there anything I can do to investigate and address this problem in virtual box before exporting to OVA and create an applicance which boots automatically in XEN.

I had the same problem when creating the virtual machine on XEN and importing into virtual box.

I thought maybe I should edit fstab to use the label rather than the uuid, but wasn't sure this is the right thing to do.