Another problem may be that the TV screen is not mapped to take a image texture, In this case I've used a single sided square positioned inside the Tv and hidden the original screen (invisible texture, I use Diffuse and specular colour black, transparency 1 trans edge and fall-off 0)

Not 100% sure of this but you could try plugging the movie node into the ambient channel then it would create light.

Re looping avi, sorry not near my poser to check, but I think there might be a loop option on the movie tab in the material room.