That is a continuing cause of lost settings.
I have a Samsung PS51D550 plasma 3D TV and in settings it has an 'eco-solution' page. The options are to turn off the tv after 15-60 mins when no input signal is received. The other options are to turn off after 4 hours if no user input is received and to dim the display according to room brightness. The tv is connected to an HTPC running WMC via an HDMI cable.
My problem is that if I set the eco-saving stuff to turn the TV off after a while of the HTPC having gone to sleep, the settings reset themselves to 'OFF' when the TV is switched back on. Just setting them to what I want and then turning the TV off and back on resets them as well.