Been going crazy with this since yesterday. I'm running a Geforce 710 using the nvidia-440 driver which I downloaded from the Ubuntu reps, and suddenly after about 3 hours of gaming yesterday, system froze, rebooted, then driver wouldn't load. Purged, reinstalled, nada. Then tried purging, checking gcc version for building .run file directly from nvidia, won't build. Purged all that work, reinstalled 440 again through ubuntu-drivers autoinstall, worked then rebooted and gone again. Tried various drivers none work. Then suddenly 440 worked again. Then rebooted, didn't work, then rebooted again and now working. I really have no clue what is happening but was inches away from putting Windows 10 on this machine. I've read hundreds of forums at this point and all recommend troubleshooting the way I have, but the problem is I'm not getting any kind of consistent results. Does anyone know what is going on here?
Ooooh! I might have just figured something out. I think this has something to do with LightDM starting before the nvidia driver loads. If I do not login, and first drop to command line using ctrl alt f1, then sudo service lightdm stop, then start it up again, it seems to work correctly. At least it did a couple times in a row for me now. I'll post here again if any new developments.