Originally Posted by pavlinux
# init 1
Thanks pavlinux and thefirstm.
I entered those commands on the console, or I rather went back to init level 1 and started X. The problem is the same, except the screen isn't completely black but dark grey and has a small horizontal line in the upper left corner (like a text cursor but not blinking). Cold reboot is the only way to get out. I attach the nvidia-bug-report but bear in mind that my first attempt at running X was just after installing v185.18.31 so it complained about a kernel module mismatch (this will appear in the NVRM messages in the kernel log).
Now in this thread other people have reported the same bug on other platform so it's more likely a v185.18.31 issue.