Comment 6 for bug 1514284

Hmm ok, it's similar to images containing spaces. The pathes are not quoted correctly by the grub scripts (/etc/grub.d/00_header in this case). This produces errors like this and also could do any type of syntax error or even bad behaviour if resulting syntax is valid.

I should file a bug at the grub developers…

Your solution: rename the image (remove the &)!