It might be easier at this point to go ahead and correct your UUIDs in your Mint and Kubuntu installs.
From either of your Linux installs, or from a live cd open a terminal and type:
sudo vol_id -u /dev/sdxx
Replacing sdxx with the drive letter and partition number of each of your partitions as now shown in Gparted. You will need to edit the /etc/fstab of Mint and probably Kubuntu also. Replace the old UUIDs with the new ones. Check to see they are labeled correctly also. You will probably need to do this in both /boot/grub/menu.lst also.
Then you can start fresh with installing grub. Let me know if you need some help installing grub. Install from the Mint install through a terminal, for both the Mint and Kubuntu installs. Don't panic if the menu isn't right. We can fix that, and will probably have to.
Think BIOS to kernel to menu to kernel. So you install the grub kernel to the booting disk mbr and tell it where the menu you want it to look at is. Then through the menu you tell it were the kernel is you want it to boot. Either the Linux kernel or another grub kernel.
The root command tells the kernel where the menu is that you want associated with that grub kernel.
The setup command tells where you want the grub kernel installed. It can be to a hard disk mbr or to a partition.
The format is:sudo grubroot (hd0,1)
----------- the menu is on the 1st drive, 2nd partition.setup (hd0)
----------- the grub kernel is installed to the mbr of the 1st drive.quit
Other root and setup examples:root (hd1,4)
----------- the menu is on the 2nd drive, 5th partition.setup (hd1,4
) --------- the grub kernel is installed to the 2nd drive, 5th partition.
If you want to learn more about grub look at the link Husse gave above or I have an example and some commentary in the below link.viewtopic.php?f=46&t=10043&start=30