I think your site's layout is not really great for ad placement, which is why that failed. It's very much a brochure like layout that you'd see for businesses. Contrast this with http://net.tutsplus.com/ where it's "blog" like, but still a great format for presenting tutorials. If you're getting 1.3 million page views, you're almost certainly ranking high in search results, which is great, because those are the people who are exploring and clicking on ads. Check out what some of the other sites in your genre are doing, I bet they optimize their design for making money with ads.