This is Microsoft's fault. The last update checked to make sure the Xbox 360 had it's original DVD-ROM that it shipped with in it (not the original firmware, although this check was done using a firmware read), and ended up bricking a lot of refurbished consoles that had their DVD-ROM swapped out. It has little, if anything, to do with firmware modding. I believe they updated the Fall dashboard upgrade to remove this check, which was ruining perfectly good systems. I'd be pissed if they ruined my system, luckily mine has all of it's original parts in it.