Cheers for the reply Rokas.
My batch (net) renders are set up to 3 external render farm nodes.
It doesn't sound like it could be the issue you mention, but i don't know much about the licensing rules for the clone plugin. I've used plugins in the past with net rendering that, you'd imagine, would require the same licensing permissions but have rendered fine.
Is this something you've heard of before? Judging by your screenshot you're just showing an example of a batch render through your own machine?