Followup to last post...problem appears to have been the DVI cable. This has been reported on other forums. The PC was configured with just a bare windows 7/64-bit install + the Intel graphics driver, and problem hit whenever driver was activated at boot. The HDMI would work, and the PC on a different DVI cable or monitor would work. I was using a new DVI cable from an NEC monitor, and an old Viewsonic LCD monitor. When I put an old cable on the Viewsonic, problem went away. I'm using an Oct/2013 version of the video driver.
This problem's been reported on other forums. It is the Intel CPU video driver, probably any of the HD 4xxxx series video.