I recently converted my Windows 10 laptop to a full Ubuntu machine. Everything was working fine until I was installing some video drivers and when I went to restart the computer it wouldn't boot properly. The Ubuntu logo shows up but then the screen starts to flash black. After that, it's just a black screen with a flashing white underscore. While the Ubuntu logo shows if I press the up arrow the last thing that shows up is "Started User Manager for UID 1000." When I press the power button the Ubuntu logo shows up again. I'm running Ubuntu 18.04 LTS. Thank you for your help in advance.