Slow progress and multitasking

At the beginning of my PhD, and especially after I clarified my research ideas, I was hoping for fast progress. As usual, it did not realize. I had a couple of alternative explanations (topic is bad, research is difficult, I'm not smart enough, I'm not working hard enough).
After some thinking, I found out that the problem is concentration and multitasking. I'm not talking about working on one idea in the morning and on the other in the afternoon (and writing a blog in the evening), but about solving a model and say, talking to your friends over IM and reading a newspaper. The multitasking killed my ability to focus, to remember and to work hard.
There is a research why, but I'm still looking for how to reverse the process.