The RROD can be falsely given if your video cable is not connected or setup right, as well as if you don't have the power cord in right or have a power surge.
Your 360 is fine, it was just a false alarm due to the setting being switched accidentally.
You can test by switching it back and seeing if it RROD's again. There are many RROD codes and I'm pretty sure one was a bad video connection.
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