I suggest you to check directly with your motherboard manufacturer in order to see if the settings are the correct ones to allow Lucid Virtu to work properly.
Keep in mind that when using this feature, it is only supported to use the monitors connected into one of the video controllers, not with a mix of both. In addition, this kind of configuration is a technology validated by the motherboard manufacturer itself, it is not something that can be called a feature of the video controller itself. It support and configuration belongs to the motherboard manufacturer and Lucid virtu.
I have done that, actually. Tech support has no answers.
Running the intel processor diagnostic tool also does'nt answer the question as to whether it is the motherboard or the CPU, as it skips the Graphics portion of the test, telling me that there is no IGPU detected, and i cannot run the test without my external video card attached (black screen).
So, I am stuck exchanging my motherboard, and if the same problem exists with the new one, I will have to exchange my CPU. Those are the only options that I can come up with. If Newegg had a refund policy on thier CPU's, I would probably go with AMD.
I do not believe that the issue would be related to a problem with the motherboard or the processor, however it seems to be a configuration issue.
I strongly suggest you to check on this with Asus* in order to check that everything is properly connected where is supposed to be and that all required settings are used.
I am having the same problem