So they haven't fixed that, huh? It was one of the missions that got broke in an update, but the others were fixed, so I just assumed this was too.
Anyway, have you done hacking before? To get thru the flying numbers/letters, it helps to have had plenty of practice. But really it's just a matter of working on getting the timing down (I failed MANY times before mastering it). For the numbers, try and find the sequence you're looking for, and set up the selection a ways ahead (the numbers move one spot to the right each tick, and wrap around). Then it's just a matter of waiting for the numbers to come to you. For the letters..... be patient (let the letter go by a couple times) and just hope you don't screw up the timing. That's about all I can say, as that's just not easy.