I had another thought regarding sde8. Perhaps the multiple entries your current menu is 'harvesting' are the older sde8 kernels which have been moved to the submenu of sde8. So although it shows just one item repeated several times, perhaps it is generating multiple kernel version entries but listing them all the same way. I would expect that a clean install of 12.04.1 wouldn't have many kernel versions, but upgrades from 12.04 would most likely have quite a few older kernels accumulated on the system.

There are a couple of ways you could check. One would be to boot into that OS and remove all additional kernels and update-grub. Then return to your default OS and update-grub and see if it changes the menu.

You could also manually edit the sde8 grub.cfg, removing not only any extra kernels that might be in the main menu but also those listed in the 'submenu' section.