Zim is a tricky one. Firstly I would discard the view that Robert Mugabe is in control. The man seems to currently be a puppet controlled by the 5 military/police leaders. Zimbabwe is currently in the control of a military Junta. The main forces in Zimbabwe consist are the Army, the Police, and a group called the war veterans (radical youth for the most part). The roles of these 3 are mixed and matched as suites the ruling party. Police often go out with the other two beating people into voting for the ruling party. If all 3 are present the reporting structure from what has filtered over the border seems to put the radical war vet youth as being in charge with the police and army following their orders as they are a pure political paramilitary organization.
As to how to resolve it the total collapse of the country is already doing that. The ruling party is already splitting apart with in-fighting over the few remaining resources. The current tri-partisan talks are a sham but already the opposition party is receiving power and recognition that they could never have hoped for a few years ago. If the current batch of power sharing talks come to nothing as I suspect they will then in the next little while we will probably see a military coup and reforms of some kind.
South Africa could have done so much more. The current quiet diplomacy approach of Mbeki is a national embarrassment. If the AU led by SA had taken a firmer line from the start then Zim could still be the bread basket of Africa as it was once known as. Its a classic case of power corrupts. Mugabe did not do all that badly in the first few terms of his rule. Its when he started staying on after his 3rd term that the trouble really began. Compare that to a great African leader like Mandela who's first act when taking office was to announce his retirement after a single term in office. President for life = absolute corruption as there is no one to answer to. If I where running SA I would remove all recognition of all African countries until they have a democratic system and a rotating presidency. I'd then do my best to economically isolate those that did not keep to that system forcing them to change. That is the only way Africa will ever lift itself out of the mess it is perpetually in.
As to the HIV/AIDS figures: In 1999 when I was based in Ladysmith the 5th SA infantry battalion had about 40% HIV infection, so the Army figures seem to be about double the national average in most countries in this area. Combat readiness of most Sub Saharan African countries is dismal due to lack of skills, racist policies, etc. According to the local press the SA air force is currently almost non-operational due to political bungling and the large scale exodus of skilled pilots and technicians to other countries (Australia especially).
As the saying goes down here: TIA (this is Africa)