thanks, I tried this one, and it leaves only the entries "Boot from Partition 3" and "OSX".
If I try to boot from Partition 3, it just leaves a black screen with the word "GRUB" and a blinking cursor....
After reinstallation of the bootloader with the Ubuntu live-CD
(boot from live-cd, open a terminal and type in:
sudo mount /dev/sda3 /mnt # sda3 is my ubuntu-installation
sudo mount -o bind /dev /mnt/dev
sudo mount -t proc /proc /mnt/proc
sudo chroot /mnt /bin/bash
..rEFIt shows again 3 boot-option:
2) Boot Linux from HD
3) Boot Linux from Partition 3
The crazy thing: both Linux-Options work!!
But after trying to delete the HD-option with your code
it again leaves the "Boot Linux from Partition 3" which is not able to boot
sudo dd if=/dev/zero of=/dev/sda bs=440 count=1
and again ends up showing a black screen with the word "GRUB" and a blinking cursor...