Comment 11 for bug 79578

It happend again right when trying to boot the first menu entry for the second time and each time after that.

Manual booting from grub command line worked without problems, but at command savedefault it sayed :
  Error 27: command not recognized

Booting an alternative entry with same kernel worked too.
(There is no savedefault)

After I disabled
   echo savedefault --default=$menuentry |
   /usr/sbin/grub_bin --batch
in some extra script in /etc/acpi/suspend.d which I have allready there since dapper and doing
   sudo grub-install
grub worked normal again. (tried one time so far)

So, the bug seems to be broken/missing support of command savedefault in /usr/bin/grub and/or grub boot-loader itself.

Changing summary