Stuck in GRUB after upgrading to 15.04

Question

I upgraded a PC from 14.10 to 15.04 today with no errors, and rebooted. Now I'm stuck at GRUB. If I select 'Ubuntu' to boot, it reboots the machine. If I go to 'Advanced options for Ubuntu' and then select an older kernel, it reboots the machine. If I go to 'Advanced options for Ubuntu' and select '(recovery mode)', it reboots the machine. If I select 'Memory test (memtest86+)', it...actually runs a memtest (all clear, by the way, breathe easy my friends).

I can get a command line, but I just can't boot the OS. Do I reload the GRUB? Use boot-repair? I've been looking for the last few hours and have found a ton of posts kinda related, but not quite the same--and they all suggest something different.

EDIT: I have tried boot-repair, to no success.

Answer 1

Test this:

Create a bootable Ubuntu DVD/USB stick.

Boot from it and select Try Ubuntu without installing.

Once you get to the Ubuntu desktop, open a terminal.

Press Ctrl+Alt+T

Run it:

sudo -i
fdisk -l

Fdisk will tell you which is your /, suppose it is /dev/sda1, continue run:

umount /dev/sda1
fsck -y /dev/sda1
mount /dev/sda1 /mnt 
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt
dpkg --configure -a
apt-get -f install
apt-get -m install
apt-get update
apt-get dist-upgrade
apt-get install --reinstall ubuntu-desktop deborphan
grub-install /dev/sda
grub-install --recheck /dev/sda
update-grub
deborphan
apt-get --purge remove $(deborphan)
deborphan --libdevel
apt-get --purge remove $(deborphan --libdevel)
deborphan --find-config
dpkg --purge $(deborphan --find-config)
apt-get autoremove
apt-get clean
exit 
umount /mnt/sys
umount /mnt/proc 
umount /mnt/dev/pts 
umount /mnt/dev
umount /mnt
reboot

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