In such case, using another partition would be a good option if there is no spare drive to test. The reason I ask this is because this is completely different from the black screen issues that have been reported, in such issues have been actually reported for HDMI, not DVI.
One thing you may test, would be the check what you see in the Intel(R) Graphics Media Accelerator control panel when both video displays are connected, and then yo try to enable Multi-monitor as shown on these articles: