Ok, so following the answer here I disabled secure boot module with:
sudo apt install mokutil sudo mokutil --disable-validation
I'm running Ubuntu 14.04 on an Asus M51AC machine. The BIOS version is dated 7/25/13 if that helps.
I can't get past the lightdm login screen (I can login via the tty terminal however). When I then change the graphics driver in a tty command line with
sudo prime-select intel, I am able to login via lightdm.
Waht is the issue and possible resolution?