This weekend's Dragon launch ended prematurely when the rocket blew up two minutes into flight, towards the end of first stage firing.
The only data on why so far is a potential issue with the liquid oxygen tank on the second stage.
Space is hard - and although landing the Dragon is still experimental, the launch vehicle itself is fairly routine at this point. Unfortunately, it doesn't take a major failure to blow up a rocket - they're tricksy beasts at the best of times.
Here's hoping it proves to be a one off or an easy fix for future flights.