If you are using a HDMI cable then there is a good chance that they have the HDMI control turned on. This is supposed to make things easier and "smart" but I found it a pain and disabled it through the set-up menu on my TV, BR player, and anything else that has it.
The only real thing us lose if you disable HDMI control is things turning themselves on and off automatically and it does not sound like that is a welcom feature to you, as it was not for me.
So check your set-up menu on your TV and look for something that says something along the lines of HDMI Control or words to that effect and it should have an option to turn it off.
We have a Magnavox Blue-Ray Disc Player that has started turning the TV off by itself about 2 months ago. We bought this from Wal-Mart back in October 2009 for $150. It has a 1yr warranty on parts but only 90 day on labor from the manufacturer. The player has parts from Funai which is who we have to contact for repairs. I thought we were having a power outage but the lights were still on in the house. Has any one else had this problem? Anyone have any suggestions? Thanx, Chewy