Grazie alla Community, ho trovato la soluzione. Due minuti e son dinuovo in pista. Sukate.
Codice:
Thanks to the community, I found - and am writing down - the steps to remove fglrx AMD/ATI drivers when you can't get to the login screen (or a terminal/console/command prompt/etc.)

Switch on your computer. Wait until the BIOS has finished loading, or has almost finished. (During this time you will probably see a logo of your computer manufacturer.) Quickly press and hold the Shift key, which will bring up the GNU GRUB menu. (If you see the Ubuntu logo, you've missed the point where you can enter the GRUB menu.)

Select the line which starts with "Advanced options".

Select the line ending with "(recovery mode)", probably the second line, something like: "Ubuntu GNU/Linux, with Linux 3.8.0-26-generic (recovery mode)"

Press Return and your machine will begin the boot process.

After a few moments, your workstation should display a menu with a number of options. One of the options (you may need to scroll down to the bottom of the list) will be "Drop to root shell prompt". Press Return with this option highlighted.

The root partition is mounted read-only. To mount it read/write, enter the command (without quotes): "mount -o remount,rw /"

If you have /home, /boot, /tmp, or any other mount point on a separate partition, you can mount them with the command (unsure if this step is needed, but unless I'm corrected by someone, I recommend you type in this command as well, otherwise you may not be able to uninstall fglrx. And, again, the command is typed without quotes.): "mount --all

Type in the following command: "sudo apt-get remove fglrx-*". Press Y to accept the changes. Ubuntu should then uninstall all fglrx drivers.

Type in the following command to reboot your PC: "sudo reboot".

Ubuntu should now reboot and use the default open-source drivers again. Cheers!