After upgrading from 13.04 to 13.10, I was having the problems described in this bug (ie couldn't mount a USB/CDROM and couldn't use GUI shutdown button) https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/851055
So I tried the solution given in post #49, which was: "The easiest fix is to switch to GDM Run these commands: sudo apt-get remove lightdm sudo apt-get install gdm Then reboot."
I did this and now Ubuntu won't load! Just hangs on a purple screen with the Ubuntu logo.
Please could someone help?! I am worried that I'll lose all my files!