I have the same 4640x Roku as the other posters and it is also stuck in a boot loop. I tried the suggestions you previously outlined. Updating, factory resetting, unplugging for 10 seconds, trying different HDMI ports or TV's... Nothing is working.
@JCameronHollis I was pretty sure you knew about it. My info was simply for education purposes for other users. I agree it is odd that so many players were affected at the same time, so hopefully Roku can identify what the issue might be. The newer player is most likely due to a different reason, as it uses a completely different chipset from the older devices, and just a coincidence that it happened at the same time. But then, stranger things have happened.
I started having the issue with model 4640. Any solutions? Was this just a bad software update? Or a technique to get folks to buy new devices?