For about the last hour South African universities (and probably other local ISPs) have experienced intermittent problems with international Internet access. These outages are the result of routing problems -- whilst we can reach the international Internet, we sometimes don't know how to route traffic to it nor does it know how to route traffic back to us. (Think of it as all the signposts randomly disappearing and re-appearing on the highways.)
The root cause of this appears to be high packet loss on SEACOM's network, and they're aware of the problem. We're told it should stabilise within the next few minutes.