I just used mobo/cpu/ram to upgrade a friend's computer and there is a problem.
It worked fine and then the video was messed up and had lines all through it and would not get past the post screen.
Could be an issue with the resolution of the card versus the monitor it's connected to. I would try a different monitor, pref. one that can do higher resolution/higher refresh rates, just to test. If that doesn't do it, try getting ahold of a cheap PCI or AGP video card. You can probably pick one up for 30 bucks.