When I boot, my computer just tells me it can't detect graphic card (or something else) settings and it has to use the low graphics mode. Then it gives me four choices, but doesn't let me choose any of them. I can get my computer to boot by going to some sort of terminal mode and then typing sudo gdm. The other graphics manager I have is lightdm. I originally had the nVidia propriety driver, and I've tried bumblebee. Mobile Intel Graphics Media Accelerator 4500M is my graphics card. Is there any way to fix this so I can use lightdm again?