Using a dual boot system since years, I always have one partition for my productive system (currently for various reasons still Karmic 9.10) and another partition to test new releases.
Recently I upgraded an Maverick 10.10 to Natty 11.04. All went well. Today I tried to do a fresh install of Natty. This failed twice (ubiquity crashed).
It turned out that the system was no longer bootable (I got a prompt saying grub rescue, neither help nor ? gave me helpful information).
I again started from USB stick, selecting rescue mode. I then mounted my productive root partitition and then issued
grub-install –boot-directory=/mnt/boot /dev/sda
On restarting the system I luckily had a proper grub list again. After some strange error messages my productive system booted.
When it was finally up and running, I again ran grub-install, this time using
grub-install /dev/sda
The mentioned strange messages are gone – may be this is a version issue (grub-install in Natty using files from Karmic).
I will retry the Natty installation but in the first place I will make a really fine backup …