Screen glitches on third text panel - whole screen on deck goes dark except for bottom right square of text

The screen kept blacking out in the start menu except for the corners where/when the cursor hovered over a menu option. Once game started, first two text panels were fine, but on third panel, screen flickered to black over all except for where the text was being read into, until it reached the end of the line, where all of the screen but for the final words were blacked out.