women leaders have some unique challenges to overcome as compared to the opposite gender... the first and foremost remains the cliche glass cieling and also the fact that women leaders need to act tough and at the same time they have maintain their feminity-- I believe these are the two greatest challenges for women leaders.
Harrasment Since the male employees fom the major population in most of the industries. Female employees are dominated by them and more than often are harrased.
I think men are naturally programmed by evolution to be more assertive and more likely to strive for positions of dominance. That is why you tend to find most leadership roles taken by men in all societies. But I do think women can be good leaders, they just seem to be exceptional.