Background/DetailsSo I just picked up an XBox 360 at Goodwill after our current one's video conked out, and had the error above. After many failed attempts at applying the update as directed on the XBox Support site, I stumbled upon a helpful video by one Mad Shark Bite that contained a key bit of information: the second set of digits is simply the update number in hexadeicmal. So I popped it in, and 3151 comes out to 12625 - which explains why my updates weren't working: it seems that for 3151, XBox support simply links to the most recent update, which as of now is 17150, far from the update my XBox was struggling with. 12625 is indeed a system update from 2011 - once I
How to Fix ItIf you're getting this error with 3151 in your error code, XBox support's link won't work. Instead, search around to download system update 12625, and follow the directions to put that on a USB drive or CD, and you should be good to go - that's what got my machine up and running again, anyway. I got my file from GameFront, but who knows how long that will last - just google with "XBox 360 Update 12625 CD" or "XBox 360 Update 12625 USB", depending on which method you prefer, and it's bound to turn up somewhere.
Once XBox Support's site is working again, I'll email them to see if they'll update it with a link to the 12625 update, but in the meantime, I'll throw this fix up here in case it helps anyone else.