The gateway people themselves posted that they were trialing anti-update code - which was causing bricking (oh wow - that sounds familiar) - they said on their website that the code wouldn't be released to the public until 100% safe - maybe they released it too early - or maybe they released what they thought was a safe subset of the code which appeared in all their tests to be ok. - but they forgot that 3DS pirate yoofs shut their consoles off in all sorts of arbitrary ways and in arbitrary situations - that their testing suite didn't cover
If this is the case, they should have released an update sooner to remove the contaminated code, but they have yet to do so.
Guessing as to what is aflicting the current firmware is a worthless feat, as they'll never publicly admit they messed up, it would be bad for business!