I seem to have runned into the same problem.
It seemed to have failed on installing software.
Error come back that it would not install it and then i could not proceed with anything else.
I believe it was hanging on the installation part.
You cannot fix this problem with the server cd.
I have tried rescuing an installation but that wasn\t working for me.
I found it extemely buggy !
You will need a live cd for this.
Start From the CD and just use hit crl+f1.
This will get you in a boot session
Then just do the following
sudo mount /dev/sda1 /mnt
sudo grub-install --root-directory=/mnt/ /dev/sda
*edit* at this point, also ensure that if /usr and /var are on seperate partitions that you mount them to /mnt/usr and /mnt/var
*edit 2* whithin the chroot you need to have /dev /run and /proc available for update-grub to work, use the following to acheive that: for i in /sys /proc /run /dev; do sudo mount --bind "$i" "/mnt$i"; done
sudo chroot /mnt
That should take care of that.
Also a warning, if you installed 64 bit you will need a 64 bit and vice versa else you will be getting an error during chroot. ( as i have )