Comment 3 for bug 1009531

Grub menu, Ubuntu, and Win7 startups are normal.

I didn't note in the previous post that running dpkg-reconfigure --frontend=gnome grub-pc did not change the output of debconf-show grub-pc. So, this looks like a mis-directed attempt by the package upgrade process to install Grub in the non-bootable Linux partition at /dev/sda6.