I would concentrate my attention on the TV that wasn't working with it. I'd also adjust my display resolution settings to see if that would help. While in display, check the dual monitor setup too.
When I try to connect to my lb7100 tv with my laptop's windows 8.1 miracast/widi, it looks like it will connect.
Then the screen will go completely black. If I move my mouse, I can see the mouse cursor on the screen but that's it. Then after about 1 minute, miracast/widi automatically disconnects.
I thought maybe lg's software wasn't keeping up with microsoft's widi software on my laptop. So I bought a Microsoft miracast adapter and plugged it into hdmi 3. I switched my tv to hdmi 3 and I can see the Microsoft adapter screen. But again, looks like it will connect, but screen will just go black (even mouse cursor doesn't show up). I tried my microsoft miracast adapter on another tv (Panasonic). No problems at all with the adapter and I used the same laptop for the test.
So what in the world is going on and how can I get miracast working on my tv? Thanks.