Re-reading the text in Glenn's image, this looks like yet another instance of bug 423247.
The workaround is to type 'fsck /dev/THEDEVICEINERROR' at the recovery shell (don't type Ctrl+D, type your root password), and reboot.
If you don't have a root password, press Ctrl+D to continue booting if you can, then get another terminal and type:
sudo -s passwd <same password twice> init 6
to get back to the boot process and its failed fsck.
Re-reading the text in Glenn's image, this looks like yet another instance of bug 423247.
The workaround is to type 'fsck /dev/THEDEVICEI NERROR' at the recovery shell (don't type Ctrl+D, type your root password), and reboot.
If you don't have a root password, press Ctrl+D to continue booting if you can, then get another terminal and type:
sudo -s
passwd
<same password twice>
init 6
to get back to the boot process and its failed fsck.