Since I was using ARD ( Apple Remote Desktop ) to manage my Mac Pro most of the time. I ended up detaching the monitor and noticed I was only able to work with a display resolution of 800x600. So I plugged in a HDMI Headless Video Accelerator from NewerTech. Now I can set the native display resolution to 1600x900 or adjust the display resolution as needed. Product can be purchased from Amazon at NewerTech HDMI Headless Video Accelerator (HDMI Dummy Plug)