At the end of the update process, clicking on the Restart button had no visible effect whatsoever. After waiting 5 to 10 minutes, I decided to reboot the computer manually.

Since then, I rebooted a good dozen times (not with the hope that it would work but with the hope of reading the messages) with the same non-result and the same symptoms:

1. I get the ASCII text-on-purple

   Ubuntu  13.10
   .   .   .   .
   

   splash screen with these messages:

   * Restoring resolver state...                    [OK]
   * Starting crash report submission daemon        [OK]
   * Starting CUPS printing spooler/server          [OK]
   

2. Everything disappears.

3. The whole process hangs at a purple screen with the mouse cursor right in the middle. At this point, I'm unable to use the mouse and the keyboard.

Booting from a 12.04 CD works perfectly, Disk Utility says that all my disks are OK and I can mount my main partition without problems.

Something obviously went wrong at the end of the upgrade but I have no idea what. I'd appreciate any pointer.

This is the kind of moment where you really think "Next time, I'll separate my /home partition for sure".

My machine is an aging but working Dell Inspiron 530 with an Intel Core Duo E2160 processor, 2 GHz of RAM and an ATI Radeon HD3650 video card.

Thanks.