Does your 6870 card have more than one digital output (i.e. DVI, HDMI) and how many of each? If it does then just get a second digital video cable and don't even use the VGA cable. I have mine hooked up using a HDMI to DVI-D on the first monitor and a DVI-D to DVI-D on the second monitor. It works much better and completely avoids windows quirky behavior associated with the VGA output.