check to see that your not running a higher res then your monitor can support. if your using an adaptor sometime they fail or dont work right. if the mb has onboard video and a gpu you may have the onboard video set as first video port so windows is switching over to it.start by seting the video boot order to gpu if your usign a gpu and try using f8 safe mode and reset the gpu video to 640 by 480.
Ok, I don't mean to sound stupid but bear with me here:
1. how do I check the resolution when I basically have no screen
2. when you say adaptor, are you talking about the connector? If so, I'm wondering if that is not the issue because I noticed the last 3-4 months that the screen would go black and I would just tilt the monitor or reboot and it would work fine then.
3. you lost me on the mb..I have a separate graphics card (if that means anything)