I love to give credit where credit is due. I got this email from iBurst:
Dear iBurster,

An incident was experienced yesterday that resulted in an unacceptable loss of quality in terms of Internet and email services for iBurst Wireless, HSDPA and ADSL valued subscribers.

The unfortunate incident was due to a break in a Telkom fibre optic cable that occurred in the vicinity of Midrand. This cable break also affected many other major South African telecoms operators.

iBurst does have redundant capacity built into our network and traffic was rerouted where possible to facilitate a quicker restoration of full service.

We sincerely apologise for the inconvenience caused and thank you for your patience.

Kind regards,

The iBurst Team
I believe this fault affected all the services that I happen to use, but only iBurst took a moment out to say sorry.