The french colonies ... I think there's problems nearly everywhere. But the worse is Belgian ones : Congo (it was Zaire something about four years ago), Rwanda and Brundi (remember 1994) ...
The problems with the former Belgian and Portugese colonies are largely due to the fact that not only did the colonial powers make no provision for decolonization, they didn't even envisage local autonomy as the British and French generally did to one degree or another. The locals had no recent practical experience in self-givernance at any level and it caused problems. Africa has been ill-served also by the general insistence that the illogical colonial borders remain the international borders in the region. Africa would be a better place today if the Katangan and Biafran secessions had succeeded. The history of Africa in the '60's and 70's would be bloodier than it was, but as a whole Africa would be more stable and represenstative today than it is.