I have the same exact issue. Upgrading to Debian squeeze. I even upgraded the grub2 package to the Debian unstable version (1.99~rc1-2) and same error.
backup:/etc# grub-install /dev/md0 /usr/sbin/grub-probe: error: no such disk. Auto-detection of a filesystem of /dev/md0 failed. Please report this together with the output of "/usr/sbin/grub-probe --device-map="/boot/grub/device.map" --target=fs -v /boot/grub" to <bug-grub@gnu.org> backup:/etc# /usr/sbin/grub-probe --device-map="/boot/grub/device.map" --target=fs -v /boot/grub /usr/sbin/grub-probe: info: changing current directory to /dev. /usr/sbin/grub-probe: info: changing current directory to disk. /usr/sbin/grub-probe: info: changing current directory to by-uuid. /usr/sbin/grub-probe: info: changing current directory to by-id. /usr/sbin/grub-probe: info: changing current directory to block. /usr/sbin/grub-probe: info: opening md0. /usr/sbin/grub-probe: error: no such disk. _______________________________________________ Bug-grub mailing list Bug-grub@gnu.org http://lists.gnu.org/mailman/listinfo/bug-grub