@Anonymous User
This problem has been discussed at length on the forum....mostly by me as I too find it very annoying. Thanks to other forum members comments we think it may affect virgin bb customers who have the older black super hub.
Please could you let us know who your internet provider is?
Another forum user managed to negotiate with virgin to upgrade to the new virgin hub (I think the white super hub 3) and this fixed the issue for them.
I have this issue on the Black box and I have also tried the app on my Samsung TV and it is the same. I have to go to the select home button to exit NowTV app and then go back in. I either get the colour balls or a black screen 
