I think you are confusing two different things. Mint uses gfxboot for it's grub graphical menu. Mint uses grub for it's bootloader. The configuration file is in /boot/grub/menu.lst. I have never used qgrubeditor, so I'm not sure which options you have set. It is better to learn how to use the command line for this type of editing. Bookmark this page and read up on grub:
http://users.bigpond.net.au/hermanzone/p15.htm It covers everything you could ever want to know about grub such as password protecting it, and customizing the menu list. To open the menu list for editing you have to have root(administrator) power. Open a terminal and run
This will open menu.lst with the gedit text editor with root powers.
"The only thing necessary for the triumph of evil is for good men to do nothing." Edmund Burke