Comment 12 for bug 589369

Thanks for performing the test. It confirmed what I was suspecting: Windows doesn't look at those signatures at all.

I therefore submitted the 'hack' upstream and it got accepted (see: http://git.kernel.org/?p=utils/util-linux-ng/util-linux-ng.git;a=commitdiff;h=01802c2e6df94aa14609d5628b276bad6bb09968 ). If/when Ubuntu will incorporate this fix, I don't know.

Regarding your mkdosfs-problem: I think that the Marantz doesn't like it when the card contains a partition-table (which you created with fdisk). What happens when you format the raw device with mkdosfs? (To be on the safe side, I've always let my devices format the cards.)