I am having the same exact problem. Same GX270, same symptoms, computer runs fine until I launch Outlook, then all is blank. That was the past week, now it will not even boot up. The A and B lights on the back of the PC next to the video port blink yellow and it makes a clicking sound upon boot attempt but nothing. I put in another video card but that did nothing. Any thoughts? How were/are you sure it was a bad motherboard? I am at odds here. thanks