What kind of TV do you have? I have a Vizio and I sometimes have that issue. I will say XBox On and it will turn on the XBox, TV and receiver. However (so far it has only happened once) it won't actually display the image on the TV. The TV is getting a signal because the screen is pitch black instead of saying 'No signal.' I've only had it since yesterday so I imagine it will happen again...
Personally, I think it is the TV because there were several times with my XBox 360 that if I turned on the XBox first, then the TV that the image would not actually load up on the TV and I would have to shut the XBox off and back on for it to work. Hopefully they will add more advanced settings like letting me give an order to turn on devices, for example first have it turn on the TV, wait a few seconds then turn on the XBox and receiver.