I have no idea why I was denied the first time. I asked my recruiter if he knew why and he said that the board wouldn't give him a straight answer as to why I wasn't picked. I just hope it goes better this time around.
Just an idea, have you considered getting a letter of recommendation from someone, other than a professor, who has known you for a long time? A family friend, a co-worker, anyone with military background/experience... I 'm not a board member, by any means, but I believe that a diversity of letters, spanning over a longer period, might look better. Right now, your professors can only attest to the past 2 years of your life.