Three secondary payloads and the main payload with its own Orion 38 motor are put into orbit, then the Orion 38, which is considered the fifth stage, fires to change the orbit of the main payload, basically a large plane change to equatorial orbit.
Seeing how everyone was pointing the finger at an engine failure until the latest data, it is perhaps not helpful to suggest causes while the investigation is at such an early stage.
It seems to be a design rather than an assembly fault. Incredibly, the drawings didn't specify where exactly the two pipes should have been routed, left it up to the assembly workers.
It was a test to make sure they could do it, and just as well since they found a problem which would have scuppered a mission where relight was needed.
I can't lay my hands on any details, but I seem to remember reading somewhere that one wartime V-2 suffered guidance failure and went straight up. Maximum altitude was over 100 miles.
It's official. The following message is on the USSTRATCOM Space-track website:
JFCC SPACE is currently working to characterize
the 16 October 2012 break up of a rocket body (Catalog # 38746)
and assess the impact of the debris field to objects on orbit. We will
continue to provide...
The mission was actually extended by a day over the pre-flight plan. The main effect of the ATO was that the orbit was lower than planned and this meant that there was residual atmosphere overhead that interfered with the astronomical observations.
The major change from two years ago appears to be the addition of the Chinese satellite.
The basic problem is that it is a very complex mission with a small budget. If you want a comparison with a similar situation, look at Beagle 2.
This was also very noticeable on the previous Chinese launch with the CZ-4B:
http://orbiter-forum.com/showthread.php?t=25134
There appears to be a layer of lightweight insulating material on the outside of the payload shroud that falls off very soon after launch.