ALERT! /dev/disk/by-uuid/xxxxxxxxx does not exist. Dropping to a shell

I am using Ubuntu 14.04.

I ran in terminal sudo apt-get update. Then I rebooted the system. And now I see:

ALERT! /dev/disk/by-uuid/xxxxxxxxx does not exist. Dropping to a shell
initramfs:_

I can't boot up LIVE Ubuntu from USB flash drive. Yes, I double checked BIOS setup and the USB flash drive is OK and runs on another machine. Right now I am going to buy a DVD and burn a Live DVD from another laptop.

sudo blkid gives me:

/dev/loop0: TYPE="squashfs"  
/dev/sda1: UUID="xxxx" TYPE="ext4"   
/dev/sr0: LABEL="Ubuntu 14.04.1 LTS i386" TYPE="iso960"   

/etc/fstab has the same UUID="xxxx" and there is a line with:

errors=remount-ro 0   

I tried using boot-repair but I still can't log in to Ubuntu.

I don't want to reinstall Ubuntu, because I have a lot of data there.

Do you have any advice how this can be solved?

Solution was to perform these commands from liveDVD, it allows me to do things on my sda1 from that liveDVD(as far I understand)

sudo mount /dev/sda1 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt
update-initramfs -u
update-grub
reboot

A friend of mine from ubuntu pl forum helped me solve this problem.

He found out that there might be error in initramfs, which should be updated as part of the kernel update. If anything goes wrong during that update problems like mine could happen.