Orbutt - I had the same yesterday. A really crappy run, sore legs, no energy. Walked several times and this was just a 6 mile run! But today I managed an 18 miler and felt pretty much back to normal. So, yours is likely just one of those unexplained bad ones, best ignored
I'm not the fear monger type, but a friend of mine visiting SA currently from New York (but he's an expat SA) was attacked by a large group of striking miners while driving to Kruger. Gunshots were fired, car is wrecked. I would again urge people to fly around SA whenever possible and avoid long distance driving.
As an expat myself, it hurts and saddens me to write that.