I was switching 360s with my dad and I needed the disk inside the console so I plugged it in and ejected it without the A/V cable plugged in. It blinked the red rings, but I did not turn it on again to test if it was broken forever because I needed to give it to my dad.
Is it broken forever? (worried)
You should test it and find out.. >_>
Meh, it probably won't do it again unless it's actually screwed up.
It won't be broken, don't worry. It will always blink red if the A/V cable isn't plugged in correctly. Just plug it in and it'll be fine.
It shouldn't have anything wrong ;)
...but if there is...I have no clue why Microsoft would make their system to do that.