On 11 December 2014 at 15:44, Tom Horsley <horsley1953@gmail.com> wrote:

When I installed fedora 21 alpha a while back, I was able
to get my nvidia GTX 750 Ti to work fairly well with binary
drivers from rpmfusion.

I've just re-installed 21 from the workstation live iso,
and all I can get with a fresh install is the screen that
says "Oh no something has gone wrong!".

So X is working well enough to display that screen, but
it would be nice to know what has gone wrong (and, of
course, I have no useful log files since systemd has
hidden all info behind cryptic binary files now).

Any clues how to investigate this?

With X in F21 there's no /var/log/Xorg*log any more so to get the X log:
journalctl -b -u gdm

(you probably already know this).

Nine times out of ten when I got that message while using the nvidia proprietary driver it turned out to be something wrong with the 3D acceleration failing due to the bundled libGL.so.* not being loaded by ldconfig for one reason or another. So check:
journalctl -b | grep accel
journalctl -b /usr/bin/gnome-session

right after you get the error message.

I hope that helps.