There are some (many?) problems with that approach, Loud Whispers. I mean, there is certainly and engineering problem in providing all the people in the world with all the food they need/want, and nothing more.
But let's jump into analogy!
There is only a computational problem in cracking any public/private key system used for confidential exchange of information. That doesn't mean we are only minutes away from reading Obama's correspondence.
End of analogy.
The engineering problem in actually a huge, huge, huge one still. For starters, while hamburger robot could provide 340 hamburgers per unit of time, there are still people in the world that don't have access to any meat whatsoever, not to mention hamburgers, and there are plenty of them. Hell, here in Poland (and we are in the EU), average person still spends more than quarter of her income on food, and let me tell you, we aren't eating fancy organic foodstuffs here. Actually organic farming is also that much less efficient, so it would make even bigger problem. I wouldn't say it is impossible to achieve post-scarcity in physical basic goods, be we are nowhere near close to that, methinks.
Actually, I have a feeling that you are a little infected with the spirit that was prevalent in late XIX and early XX century in physics. Don't take that as insult, as I understand the sentiment, but I'm on a very different position here.
Also, don't forget that there are some non-reproducible goods both material and immaterial, that are more than an engineering problem; for example, first row seats at cultural events; paintings and sculptures; and other that don't came to my mind right now (you monsters you).