My machine had red flashing light in the bottom right - E47 error appeared on screen
Most online suggestions were to unplug all power cables and harddrive and reconnect - did this a bunch of times and issue persisted.
Bought the X-Clamp kit off eBay for a few quid and replaced them on my machine - after a few re-boots it now works perfectly fine. not sure it's a permanent fix tho.
IF you're yet to take the machine apart you may qualify for the E47 warranty extension from Microsoft, double check that first. If not try XClamp fix, worst comes to worst you're still gonna have a broken xbox :P