I've also been having this problem, what happens is when I start my computer, I'll get the windows vista green progress bar, then instead of showing the glowing windows logo then taking me to the logon screen, I just get a black screen, and my monitor light flashes on and off. I have to restart my computer before getting the logon screen, then it's fine. Also, the problem seems to occur when I lock my computer and come back after a while the monitor will not display anything even though I try to resume using my mouse.