Extended display recognised, but blank

[mistresswebb77]

I have a TV I want to connect to my laptop as an extended display. I've connected them with an HDMI cable (which is not broken, I've checked). My laptop picks up the extended display as Beko-VJAZ1. The tv is set to the correct HDMI channel, and the screen works (it displays the channel number, and I can view all the menu's on it). The laptop is happy the other display exists, and I can move windows as though I am dragging them onto another screen. The only problem is, the TV display is just black. It doesn't show my wallpaper as it did when I had this set up before, and any windows dragged onto that screen do not display. Does anyone have any thoughts what might cause this, and how I can resolve it please?

My laptop is running Windows 8.1 pro, 64 bit intel core i7-3820Qm CPU @ 2.7ghz
My display adapters are Nvidia GEforce GTX 670M and also Intel HD graphics 4000

Many thanks!

 

[ElectrO_90]

Maybe you need to slow down the Refresh rate?