[ubuntu] Cannot boot into Win 7 after reinstalling GRUB: I get "Error 13" (details below)

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http://ubuntuforums.org – My machine has 2 separate physical disks, one for each OS. Windows (sda) and Ubuntu Linux (sdb). My Windows disk had "Vista Business x64" and the linux disk has Ubuntu 12.04. I recently upgraded Vista to "Win 7 Pro x64" and as expected, it screwed with the MBR and GRUB was not coming up at boot up time. So, I reinstall GRUB and go through the whole 9 yards (Booting from live CD and mounting the boot partition, reinstalling GRUB). Please note that I installed GRUB only on 'sdb' and I changed the boot sequence (in BIOS) to pick 'sdb' as the first disk (because o/w GRUB will n (Hardware)