I tried to install Ubuntu 12.04 on the partition where I had Ubuntu 10.10, by first formating the partition (ext4) and keeping the same partition settings (the mount point is '/').
I use the Ubuntu installation disk I made on a USB drive.
Installation went fine until an error indicating a failure in APT configuration from the CD .
And now the system isn't bootable anymore :
Grub error, file not found
What can I do ?