I found
this article at the autosport site. It in turn quotes from a Gazzetta dello Sport article. Kubica's co-driver, Jakub Gerber said, "We knew the surface was slippery because of the humidity and we were ready. After skidding, the car leaned against the guard rail and pushed it outwards. Then it crashed against
the following guard rail.
"The guard rail pierced through the car and went all the way through it. I immediately saw it was serious, he also had a bad bruise under his eye after hitting the steering wheel. Robert passed out and I exited through the window because the door was stuck.
"The ambulance arrived immediately and then came the firemen. They took over half an hour to pull him out. The first crew didn't have the shears so they had to wait for another crew. Then the helicopter couldn't land in that spot, so Robert had to be moved and more time was lost."
Gerber was critical of the section of road that had a gap between two sections of barrier, leaving the end of the second exposed. And he also called for increased protection around the cockpit of rally cars.
"That opening [between the two sections of barrier] makes no sense," he said.
I bolded the bits that seem most pertinent.
So... if we can accept that description, it appears that Byronrhys's term "Incorrectly installed armco" about sums it up.
Oh and yes, pardon me if this point has previously been made. There are 474 posts in this thread so far and, well, life's too short.