DeltaBurnt said:
Sounds like your first problem could have been caused by:
1. Bad card, it could have been on the way to dieing make sure you don't use card readers included with the M3 products I'm not sure if the newer one for the M3i Zero does this but it can slowly kill your card. Just a heads up, I think it might be fixed with the new ones not sure.
2. You got one with bad contacts (if that were so it might not have even read it in the first place) and it's the manufacturer who sent you a bad card if it wasn't "bricked" yet you could have gotten a new card you might still be able to with this explanation (don't include that it's "bricked" though, if you mention it they might say that there's no way for them to see if there's something wrong with it but this isn't technically tricking them this is just you getting your money back for a card that didn't work).
Now for your second problem:
1. The power cable might have been damaged causing it to not give it as much power as it needed so it was taking really slow to update or it couldn't start it at all because it was using all the power to make the LED blink.
2. Faulty updating unit?
Other than those two reasons I can't think of why it may have been blinking for an hour, try contacting the retailer where you got your M3i Zero from.
u may have the wire in the wring way, i did it twice
make sure the back of the card points up, the light will start blinking then,
its a weak card so turn on your Ds and put it in while its on may help & don't forget to put sakura on it while flashing it some how made mine work, as i flashed mine twice to get it to read.
just got mine today and there the problem i've had / fixed.