unsupported video format

I had window 7 for some time and recently upgraded to a 42" sony 1080p tv I use a Lenovo computer with a NVIDIA GeForde 930 GE apadter. I've adapted it fine to fit perfectly however every few weeks it comes back on with a black sceen on my sony 42" and tells me it's an unsupported video format, I then have to bring out another smaller screen I have lying around (luckily) plug it into that reset it, then plug it back into my tv and reset that. why is this happening, more ompoartently how do I stop it form happening? thanks