Receiver shutting down during high loads

The first thing I'd check is whether or not you have a "dead-short" between speaker wires! This will cause the receiver to go into a shutdown/"protection" mode in most models. Might check that. Also, yes, did you change speakers? Do you run the speakers as "full range?" Might check all this. Receivers have limited power output mostly, and most often than not "small" is the better speaker setting, sending the demanding bass to the subwoofer. Check it all. If all else fails, send the unit for inspection.

Thanks Flrnlamb and Elevick, I have not changed speakers for at least 7 years (KEF Coda 7's as mains and simple JVC surrounds without a sub). I did choose "small" on center speaker, I have the level at MAX, but I've had it there for the past number of years with no problems (until now). I am adding a subwoofer, so I don't ruin my Coda 7's, but since I haven't had one, and haven't had any problems until now, I don't think that's it...
I have run the speaker check mode, and everything seems to work, no negative polarity issues, but I must admit I don't know what a "dead short" is or how to check for that...
It certainly seems as though it goes into a shutdown/protection mode. Again, this is a brand new problem--it's worked flawlessly for 7 years or so...

As an update, I watched the scene again (scene 7, The Interpreter) and everything sounded fine for about 3 minutes when the audio seemed to drop out by maybe 50%...30 seconds or so later the receiver shut down... I believe it may need new capacitors as I cannot find any shorts in my speaker wires. Also Elevick, it is a 110v unit with no external transformer.

Another update, the repair shop said this looks like a digital problem. Does this sound right? The unit overloads in Prologic as well...