wpegg: How would you go about fixing all this?
I don't have a particularly good answer to that. The difficulty is that the transition from what's essentially tribalism to the modern concept of a nation is one that usually takes hundreds of years of incremental societal developments, and "fixing" the current situation basically means trying to cram those hundreds of years of development into just a few years.
If the geographical distribution of the few major groups is favorable then splitting up the country to separate those groups would make sense, although you'd still need to deal with the issue of needing to facilitate the relocation of minority groups, otherwise they'd likely suffer repression and violence at the hands of the majority group. However, even after doing this it would likely be necessary to have an international military presence at the border between the two new countries to prevent violence and possibly full on war between the two new countries.
However, the geographic distribution is rarely so clean that this kind of approach could be taken. In such a situation, a lasting fix would require a societal attitude shift that would likely take at least 30 years. A strong military/police presence would be needed during this time to keep things from falling apart, along with massive investment in both infrastructure (to bring the country together physically) and education. The goal of the strong emphasis on education would to be to instill the cultural values necessary for a lasting country in the younger generations while essentially waiting for the older generations (who are likely set in their ways) to die off. This all requires a massive and lengthy investment that it would be very hard to convince any country to undertake (since they'd be getting very little out of it compared to the investment) which is why you're not seeing this approach taken.
The more realistic approach is to basically just try to keep the situation contained- prevent it from spilling out to other countries and keep it from getting too bad internally. This would be done by backing at least a somewhat moderate, non-terrible leadership, and providing enough aid in various forms to keep that leadership in power and keep the situation for the citizenry from getting too bad. This is pretty much the approach that's currently being used and while it won't do much to fix the situation it at least tends to keep it from spinning out of control too quickly (although there's no guarantee, as the current situation in Iraq shows).