WDS pending devices-> Name and Approve->create new Unattend file failure

Hi there, i installed WDS in my test environment and always have that failure when i try to install an Image with the unattend file which you can create in the "Approve Pending Device Wizard".

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When i dont use that wizard everything works fine, but when i try to minimize the imput before the Installation i get that message.

I think, the Problem is, that the Partition is not formated?! Is there a way to solve that Problem, beside writing my own unattend file. Is that a bug in W2012?

Thanks

Andy