memtest86 and grub-probe error "no such disk"

[scar]

i am working through an upgrade from 10.04 to 12.04 and dpkg is having a
problem setting up memtest:

# dpkg --configure -a
Setting up memtest86+ (4.20-1.1ubuntu1) ...
Generating grub.cfg ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when
GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-3.2.0-68-generic
Found initrd image: /boot/initrd.img-3.2.0-68-generic
Found memtest86+ image: /memtest86+.bin
File descriptor 3 (pipe:[16217]) leaked on lvs invocation. Parent PID
3623: /bin/sh
grub-probe: error: no such disk.
done

and then it just hangs there until i ^C

if i try to run update-grub it at least doesn't hang:

# update-grub
Generating grub.cfg ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when
GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-3.2.0-68-generic
Found initrd image: /boot/initrd.img-3.2.0-68-generic
Found memtest86+ image: /memtest86+.bin
umount: /var/lib/os-prober/mount: not mounted
rmdir: failed to remove `/var/lib/os-prober/mount': Device or resource busy
rmdir: failed to remove `/var/lib/os-prober/mount': Device or resource busy
rmdir: failed to remove `/var/lib/os-prober/mount': Device or resource busy
rmdir: failed to remove `/var/lib/os-prober/mount': Device or resource busy
grub-probe: error: no such disk.
done
#

there's a lot of google results but none of them seem to pertain to my
situation; there's no /boot/grub/device.map file to remove, etc...