Stuck in protect mode

More than likely a blown channel.

Your device has went into protection mode, an internal malfunction causes it to shut down in order to protect itself.
Somtimes a physical reset will help.
Turn of and unplug device fro a couple of hours

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If you do not hear the protection relay click, then replace the relay.

It sounds like the output ic's may have failed, because of the complexity of system I would have a professional come and look at the unit for an evaluation, chances are he will need to take it back to the shop for service.

Contact Sony website - usually a malfunction in the unit requiring service, and you cannot reset it. HOWEVER, try the usual unplug, wait and plug-in again. Make sure that there's not a shorted speaker - so unplug all speakers and try using just headphones. Also, make sure you have air ventilation around the unit - nothing on top of it, as that will cause it to overhead and shutdown. Try these items and report back. Good Luck!

Follow the steps below to troubleshoot if PROTECT or PROTECTOR is flashing in the display of the A/V receiver:
IMPORTANT: If model-specific information is required to complete any of the steps in this solution, refer to the operating instructions supplied with the product. Manuals are available online in the Manuals/Specs/Warranty section of the Sony® eSupport Web site.
NOTE: Because each of these steps represents a possible solution to this issue, check the A/V receiver status after completing each step.

1. Check the speaker wires and speakers for proper connections.
2. Reduce the volume level. IMPORTANT: If the A/V receiver is used at maximum volume level, it may enter the PROTECT mode. Maximum volume listening will cause the A/V receiver to run very hot and may drain the output capacitors.
   
3. Disable the surround sound option if both the A and B speakers are being used simultaneously.
4. Ensure the top of the A/V receiver has proper ventilation to keep it from overheating.
5. If the message only occurs when using a DVD player, the sampling frequency may be set too high. IMPORTANT: Some A/V receivers provide compatibility with the higher sampling frequencies through alternate connections. Consult the owners manual for specific information.
   
6. Unplug the AC power cord for approximately 1 to 2 hours to reset the output transformers.

If the issue is still unresolved, service may be required. The Sony® eService Web site at http://eservice.sony.com/ can assist you in obtaining service from a Sony Service Center or locating a Sony Authorized Servicer.

Protet mode is a special diagnostic mode that starts when a fault is detected.

When in protection mode the unit is prevented from starting by protection circuit, so to prevent further damage.

Check the speakers and speakers wiring, a contact in speaker wires, or faulty speakers can send the unit in protection.

Try unplugging power cable for one hour or so. then connect cable back and see if you get rid of protect state. Sometimes accumulation of electrostatic charges inside circuit capacitors can kick in protect mode. In that case unplugging the unit from main for some times can get rid of electrostatic charges, and reset circuits by draining power completely.
If that was the problem, you will not get Protect when plugging back power cable.

If you do all the above and still get Protect, then there is a real fault.

In that case the unit may be disassembled and tested to find the fault.

If that is the case I suggest contacting the manufacturer at the number listed on the owners manual, or asking a quote on repair to a local technician.

Protet mode is a special diagnostic mode that starts when a fault is detected.

When in protection mode the unit is prevented from starting by protection circuit, so to prevent further damage.

Check the speakers and speakers wiring, a contact in speaker wires, or faulty speakers can send the unit in protection.

Try unplugging power cable for one hour or so. then connect cable back and see if you get rid of protect state. Sometimes accumulation of electrostatic charges inside circuit capacitors can kick in protect mode. In that case unplugging the unit from main for some times can get rid of electrostatic charges, and reset circuits by draining power completely.
If that was the problem, you will not get Protect when plugging back power cable.

If you do all the above and still get Protect, then there is a real fault.

In that case the unit may be disassembled and tested to find the fault.

If that is the case I suggest contacting the manufacturer at the number listed on the owners manual, or asking a quote on repair to a local technician.

Yep. The wiring to your speakers or the speakers themselves have shorted out. You have a blown fuse. You'll need to either replace the unit or attempt to replace the fuse yourself.

You may have loosened a solder joint on one of the components inside with your air blast. A repair tech would monitor the outputs DC offset voltage and he will probably see one that is not zero volts and while wiggling various things he should see a sudden change in the DC offset voltage on the bad channel when he touches the bad connection. Then it's just a matter of resoldering the connection. Good luck on this one.