14.04 - NVIDIA Drivers are not working anymore - only 1 screen is detected, max resolution 800x600 - Ask Ubuntu

i'm stuck @ problem can't solve myself. recently, obs (open broadcast software) stopped working, i've decided test little bit around fixed.

i've done update, upgrade, dist-upgrade , -f install , did several updates, including linux header updates seem make problems.

after reboot i've had 1 single desktop use, , max resolution 800x600. also, nvidia x server-window hasn't more settings available before (only 2 options now, both useless).

i've purged nvidia-packets reinstalled nvidia-304 , nvidia-352 (i wasn't sure 1 need, since have gtx 780 - or 740, not sure right now). both didn't worked.

so basically, in short, here's problem:

• having gtx 7xx graphic card
• using ubuntu 14.04
• recently updated linux headers trough apt-get dist-upgrade
• now having bugs graphic engine.

how can fix this, , how can appropriate drivers working?

thank much.

first remove installed nvidia software.
select ubuntu menu entry , press e key.
add nouveau.modeset=0 @ end of linux line.
press f10 key boot ubuntu system.

when login screen appears press ctrl+alt+f1.
enter user name , password , execute :

sudo apt-get purge nvidia*   sudo reboot  

install latest stable drivers gtx 7 series cards.
select ubuntu menu entry , press e key.
add nouveau.modeset=0 @ end of linux line.
press f10 key boot ubuntu system.

when login screen appears press ctrl+alt+f1.
enter user name , password , execute :

sudo add-apt-repository ppa:graphics-drivers/ppa sudo apt-get update sudo apt-get install nvidia-367 sudo reboot   

note : set space between last character in linux line , nouveau.modeset=0.
after nvidia drivers installed adding boot parameter not necessary anymore.
when want install latest official drivers, replace nvidia-367 nvidia-370.