Ubuntu always adds new items into the grub without removing the old ones after upgrades.If you have this problem and want to clean up old entries from your grub menu,this tutorial may helps.
Edit the file /boot/grub/menu.lst by following command in terminal:
sudo gedit /boot/grub/menu.lst
Find out the line which says “#howmany=all”,change it to “#howmany=1″.Close and save the file.Next time grub menu boots up,the newest kernel lines will be shown.
If you just want to delete the one entry in grub menu,also in the above file find the section start as “## End Default Options##”,find out the part and delete it.