I have a Z68 Extreme4, BIOS version 2.20 with a Core 7 2600k, 16 GB RAM, running Win 7 Ultimate x64. I am using the onboard Intel 3000 graphics, dual monitor configuration, no discrete graphics card. It's been working fine for a year or so, but now I can't get any output on the DVI-connected monitor. In the Intel Graphics and Media Control Panel, it won't allow me to select a multi-monitor configuration. When I try to apply a previously saved profile that has dual monitors, I get an "Invalid Profile Warning: this profile cannot be applied with the existing setup."

I've tried rebooting, reseating the cable connectors, connecting with a different cable and a different monitor, but nothing makes a difference. I tried upgrading to the latest VGA drivers on the Intel website, and also reverting to the latest version on the ASRock web site. I tried rebooting with only the DVI connected. I checked the BIOS settings, but didn't find anything that seemed to be related to disabling one of the video outputs. Seems that whatever I try, I can't get any indication that the DVI port is alive. The system is otherwise fine, and I am not seeing anything wrong on the VGA-connected display. Just can't get that second monitor to work again.

Any ideas on what's wrong, or how I can debug things further?