What?(message about my DVI-D cable isn't plugged in keeps bouncing around on screen): it is normal because the gpu has stopped sending signal to your display. In this situation the minitor should show this message. have you recently changed anything your monitor menu? If not do a reset of your monitor settings menu or check the power saver option. There will be a option regarding power off time. In my lg monitor it is there. If nothing fruitful then check with a different cable hdmi or something but I am sure it is not the cable issue.