is there anyone that can tell me why my tv tells me itunes is not switched on in the computer but it is.

i can use my apple tv to play music from my computer, to have my photo stream on the tv, and watch youtube and all the other channels but not the movies from itunes. this does not happen all the time but a lot of the time. it shows that films are coming through, but on the living room connection it is just speakers no tv. what am i doing wrong, it is a great gadget to have because i can change all movies to fit onto itunes, using wondershare converter, great for d/l from y/tube etc and converting music and films. but i am finding it so hard to find a reliable connection between my apple and my pc for movies. hope for some help. HELP. oh by the way got windows 8 now.