I also had a similar issue with the grub menu list, and here's how I fixed it.
The file /etc/default/grub.d/50_kubuntu.cfg
passes on "Kubuntu" as the name of the distribution to update-grub
. If you want to change it back to Ubuntu, the fix is as simple as:
sudo rm /etc/default/grub.d/50_kubuntu.cfg
sudo update-grub
If you want to change it to something else, just edit /etc/default/grub
and change the GRUB_DISTRIBUTOR
line to whatever you want. Example, change:
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
to:
GRUB_DISTRIBUTOR="My very own Ubuntu install"