sys-boot/grub and app-emulation/xen both use mount-boot.eclass to automatically mount /boot prior to installing files there, but <=sys-boot/grub-static-0.97 blindly copies files to the /boot directory, even when /boot is a separate partition and hasn't been mounted. Adding "inherit mount-boot" to the grub-static ebuilds is the only change required to address this problem.
sorry, fixed in cvs