I have had my Samsung 46" plasma for at least 5 years,every time I put my ps3 on,it swithes the TV on/off.I tried 5 new hdmi cables and got a new ps3 and it still does it.it funny my xbox works fine on it.

Are you using a infrared controller or a wireless controller with your PS3?

I have a wireless controler

i have a wireless controler

That may be the problem. Have you tried using the old style (wired) and see if it happenes with that?

If it doesn't you have found the problem.

Turn off HDMI-CEC. You'll find it labeled as AnyNet on the TV's settings.

Also turn off HDMI control in the PS3's options.