Four red lights on a Falcon Xbox 360

My secondary Xbox 360, a Falcon, shut off yesterday during a game and displayed all four red lights flashing rapidly. After turning it back on, it booted as usual and then after a few seconds shut down again and presented the same fault indication. I checked all the cables and found them to be firmly installed. The Xbox 360 is connected with a High Speed HDMI cable. There is no audio breakout dongle attached, only the HDMI cable.

I also let this Xbox 360 run for about half an hour today idling on the dashboard, and it did not present an error.

Prior to this, the console had been left unused for several weeks and received the last (pre-Metro) system update. It had also inherited a 250GB HDD previously used on another system, and left blank after its contents were transferred onto an Xbox 360S.

From my understanding, the four red lights indicating an error with the AV cable happens only on non-HDMI Xbox 360 models (Xenon and Opus), and should not happen on the models with HDMI (Zephyr, Falcon, Jasper, and Valhalla) regardless of which connection type is used.

Also, from my testing today it appears that if the HDMI connection is interrupted, the Xbox 360 will simply attempt to reestablish the handshake with the sink in the receiving device, and not shut down or reset. If the connection of the regular AV cable is interrupted or its status changed on the Xbox 360 end (e.g. if a component cable is switched from SD to HD mode), the Xbox 360 will simply perform a reset without indicating any error.

All those things combined lead me to believe that this error indication has nothing to do with the AV output itself, but it could indicate something more sinister such as a problem with the HANA, GPU, HDD or the power supply. Given that the console is out of warranty and I already have recently upgraded to an Xbox 360S, I probably won't bother submitting the Falcon for repair but scrap it. Still, it would be nice to know what this error indication is actually trying to tell me.