Sorry, Bryan, I don't have an answer for your question. What I can tell you, though, is that I just ordered Ed Strachar's tape-course Magical Concentration from Nightingale Conant, as I have problems concentrating too. I have also started doing Brain Gym exercises to see if this helps. I'll post back later when I know whether these things are useful or not. Ed Strachar's other courses have gotten mixed reviews, but we'll see anyway.
If anyone else has any good tips on what to do with this problem, I'll be very, very happy indeed. It's really the one thing that's holding me back the most in my life.