Brains are complicated, not magic. But complicated is bad enough.
So would you consider this blog post in accordance with your position?
I could believe that coding an AGI is an extremely laborious task with no shortcuts that could be accomplished only through an inordinately large number of years of work by an inordinately large team of inordinately bright people. I argued earlier (without protest from you) that most humans can't make technological advances, so maybe there exists some advance A such that it's too hard for any human who will ever live to make, and AGI ends up requiring advance A? This is another way of saying that although AGI is possible in theory, in practice it ends up being too hard. (Or to make a more probable but still very relevant claim, it might be sufficiently difficult that some other civilization-breaking technological advance ends up deciding the fate of the human race. That way AGI just has to be harder than the easiest civilization-breaking thing.)
Here's a blog post with some AI progress estimates: http://www.overcomingbias.com/2012/08/ai-progress-estimate.html
Claim: The first human-level AIs are not likely to undergo an intelligence explosion.
1) Brains have a ton of computational power: ~86 billion neurons and trillions of connections between them. Unless there's a "shortcut" to intelligence, we won't be able to efficiently simulate a brain for a long time. http://io9.com/this-computer-took-40-minutes-to-simulate-one-second-of-1043288954 describes one of the largest computers in the world simulating 1s of brain activity in 40m (i.e. this "AI" would think 2400 times slower than you or me). The first AIs are not likely to be fast thinkers.
2) Being able to read your own source code does not mean you can self-modify. You know that you're made of DNA. You can even get your own "source code" for a few thousand dollars. No humans have successfully self-modified into an intelligence explosion; the idea seems laughable.
3) Self-improvement is not like compound interest: if an AI comes up with an idea to modify it's source code to make it smarter, that doesn't automatically mean it will have a new idea tomorrow. In fact, as it picks off low-hanging fruit, new ideas will probably be harder and harder to think of. There's no guarantee that "how smart the AI is" will keep up with "how hard it is to think of ways to make the AI smarter"; to me, it seems very unlikely.