Comment 22 for bug 82312

For the benefit of others who spent ages tracking this down: next time
something weird happens to your video display, dive straight into
/var/log/Xorg.0.log and do your best to make sense of it.

The penny dropped for me when I saw no error (EE) lines at all - as
far as X was concerned, everything was working just fine (which would
explain why the login screen's drum sound happened as expected, and
why I was still able to switch consoles with Ctrl-Alt-F1 or cause an X
restart with Ctrl-Alt-Backspace).

But there was a line saying "Assigned Display Device: CRT-0" in there,
and it occurred to me that not only was my flat panel completely
black, but the backlight was turned off, as if X had been told to use
an entirely different display.

Googling "xorg options nvidia" got me here:

http://http.download.nvidia.com/XFree86/Linux-x86/1.0-8774/README/appendix-d.html

and a quick edit to the URL to match the nvidia driver version from
Xorg.0.log got me here:

http://http.download.nvidia.com/XFree86/Linux-x86/1.0-9631/README/appendix-d.html

and the rest was straightforward.

I still don't understand why, left to its own devices, the nvidia
driver autodetects a CRT when there isn't one connected but doesn't
detect my TV-out port at all; is this a Dell BIOS thing? It's good to
have options available to override all the automatic behaviour,
though.