Has anyone had success with the googlebase isbn/upc feature?

I activated the upc/isbn feature. The isbn number uploads in the feed but in my google merchant account, in the feed errors, google recognizes it as an invalid upc number.

My feed shows the isbn number in the correct field

<g:isbn>0517093103</g:isbn>

This was a few months ago and I had asked about it on the google boards and never got a resolution.

I'd love to hear about the experience others have had with it.