I just tried updating to 13.04 from 12.10. When I restarted, it went to Grub even though there's no other OS on the computer. I clicked on Ubuntu to finish booting and I got a terminal with the error message:

General error mounting filesystems.

A maintenance shell will now be started.

CONTROL-D will terminate this shell and reboot the system.

root@mycomputer:~#

Reboot brings me back to the exact same place.

The only other options on Grub are Advanced options for Ubuntu and a couple of memory test options. I ran one of them and it came out fine.

I have no idea what to do next. Please advise.

EDIT:

Per request, here is the contents of /etc/fstab:

# /etc/fstab: static file system information.

#

# Use 'blkid' to print the universally unique identifier for a

# device; this may be used with UUID= as a more robust way to name devices 

# that works even if disks are added and removed. See fstab(5).

#

# <file system>  <mount point>   <type>   <options>        <dump>   <pass>

# /was on /dev/sda1 during installation

UUID=5b22f712-cd92-446e-8984-0c31ca17c02c /                ext4     errors=remount

-ro 0       1

# swap was on /dev/sda5 during installation

UUID=86ea10b7-9309-4860-8ade-059f9d9fa328 none             swap     sw

  0       0