I fixed it by exiting full screen and placing cursor on to Now TV border. Obviously not an acceptable solution and I will be asking for a refund of Pass. Just updated Now TV and did not have this problem last time. Problem last time was badly pixelated screen. Cannot believe how bad this service is. You used to be able to buy Pass straight to Sky Box. Nothing like improving a service to customers.
I just had this issue on a windows PC and it seems to have been because I was running "Speccy" a hardware monitoring program. I stopped running the said program and all was well again. So maybe check what other processes you have running. Hope this helps someone.