Career Advice

Mark,
I need your advice on a situation that I am facing at work. I am currently in a role that I have been told is important for the organization. I dont believe its the best use of my skills but like a good corporate soldier I am willing to do it. I believe I am very effective in this job and the results speak for themselves. I also have a number of directs who are happy with me. I have a very good relationship with my boss and he has been responsible for my growth monetarily and organizationally. He does not follow any good managerial feedback or review processes. I have overlooked all that because he has generally taken good care of me.

I have been talking to him for about a year now about a promotion. He has been telling me that I am 'ready' for the next level and that its going to happen. Well when it was time for it to 'happen', nothing happened. I talked to him about it and he pulled a mea culpa. He told me, in not as many words, that he dropped the ball and did not follow up on it the way he should have. I believe that because I know him to be very disorganized and this would not be the first time he let something fall through the cracks.
I feel extremely let down and would like to give up my current role and take up one where I know I can really make a huge impact (for my own career). This new role would still report to him but it would involve me working in an area that I prefer rather than doing something that the organization wants off me. I would have to give up all my directs and move into the role of an individual contributor. While my decision may create some short term problems for the organization, I feel that it will greatly enhance my own skills and marketability.

Do you think I would be committing career suicide by taking this step? How would you proceed if you were in my situation?

Thank you.