TV power up to screen saver

I'm curious if anyone else has seen this. I have had a Contour box connected to a Samsung flat screen TV for about 2 years. I've been powering down the box using the verbal command - press the microphone button on the remote control, say "Power Down" or "Sleep Now", which brings up a dialog box from which I select "Sleep Now". After about five seconds, the Contour box and the television will turn off. This has worked fine until about 2 weeks ago. Since then, after initial power down, and after a pause of about 20 seconds, the TV comes back on and displays a screen saver, which stays on indefinitely (I've awakened in the morning to find it this way). Apparently, the TV is receiving a signal from the cable, even though the Contour box power light is off. Anyone have any idea what's causing this?