GRUB installation fails with mini.iso

[Brian <claremont102@gmail.com>]

I installed a recent mini.iso to a USB stick with

   cat mini.iso > /dev/sdX

and went on to put unstable on the same stick. GRUB was unable to
install to /dev/sdX and reported:

   hd0 appears to contain a iso9660 filesystem which isn't known to
   reserve space for DOS-style boot. Installing GRUB there could result
   in FILESYSTEM DESTRUCTION if valuable date is overwritten by
   grub-setup

Doing

   dd if=/dev/zero of=/dev/sdX bs=512 count=2000

prior to partitioning solved the problem.

Whether of not d-i could or should cope with a boot sector processed by
isohybrid I would suggest some documentation would not be out of place.