Hello to all, I had the same problem with my 18 month old KDL series 46" Sony. The remedies mentioned on this forum are all really good ones. If, for some reason, these remedies don't work for you try this remedy. Turn off and unplug the power cord for ANY HDMI connected to your TV, including your TV. Wait a couple of minutes and then, one device at a time, depress and hold the power button on each device for about 30 seconds. This will allow the capacitors in each device to completely discharge. The capacitors hold a charge, after they are unplugged, which allows the "error" to stay in the device's memory, holding the power button allows the capacitors to discharge. Then the "handshake protocol" between HDMI input and your devices can be re-established. If the other very good information in this forum doesn't work then give this a try. KUDOS to all that post on here, its my first visit and its a nice site!
Good Luck to all!