So you're having a problem with the protected mode with your Sony receiver. The protected mode kicks in when there is a safety issue with the receiver. This usually comes from an overload to the system via a short in the system or perhaps a surge in power. Your receiver shuts down, and you'll need to shut the entire system down to fix it. At minimum, this is very annoying, especially while watching a movie. At maximum, you could be doing permanent damage to your system.
Check Power Surges
In some older homes, some of the wiring doesn't deliver the "cleanest" power, delivering minor power surges to the items you plug directly into the wall. If your receiver is plugged directly into the wall, purchase a surge protector to stop this.
Choosing the Right Surge Protector
There are almost as many surge protectors as there are misconceptions about them. You will need to choose a surge protector that offers a warranty if your items break due to a power surge while they are plugged in, usually $10,000 or more. Belkin is a particularly good brand, as they give you good value for your money.
Adjust the Speaker Wire
Your Sony receiver probably has at least five speakers and a subwoofer plugged into it. On the back of your receiver, unplug one of the wires. Twist the threads of the wires tightly together and reinsert. Repeat with all the wires on the back of the receiver, then on the individual speakers.
Switch Wire Plugs
Your receiver could be receiving surges because your wires are plugged into the wrong holes. Each of your speakers has two plugs that are color-coded, one black and one another color, usually red. This corresponds to the plugs on the back of your receiver. Ensure that the half of the wire plugged into the black hole is also plugged into the black hole on the receiver.
If the problem continues...
If the problem continues, you need to start replacing your speaker wires. Unplug each speaker to test and see which one is causing the problem. Once you've determined which wire is causing the problem, you'll need to replace it. Use a high-grade speaker wire, preferably Monster, which uses high-grade fiber optic wire that rarely has shorts.