Esther Derby has a blog entry about natural born leaders and managers vs. learning the skills (she also has a link to a nice little article called “Do We Have to Choose Between Management and Leadership?“).
I agree with Esther that you can learn the skills of both management and leadership. However before learning comes awareness and openness. Some managers I came across so far haven’t had either.
If you are not aware of the lack of (at least some) of the skills, you have no chance to learn. The same holds true if your are not open to the different aspects involved in becoming a great leader and an effective manager.
A mindset of “you can always do better” definitely helps to become a better manager and leader. If that is not the case, you have to rely on your current “natural” skill set, whatever that is.