from F1.com
not 100% sure what they want to say with the highlighted part, but it sounds a bit like flexure in the wheelbearing/upright to me - under lateral/cornering load.Formula1.com wrote: After several reliability issues, Red Bull's chief technical officer Adrian Newey has changed the positioning of the RB6's front brake calipers. Instead of the horizontal position, which lowered the suspension's centre of gravity, he's moved the front calipers back to the more standard vertical position. The previous positioning had led to occasional mechanical failure due to greater movement of the brake pistons, pads and discs. This was a change planned for 2011, but the team took the decision to run with it for qualifying and the race in Japan.
I can see, that this causes some problems, but not sure why it would lead to mechanical failures. It also seems to be only a problem at the front, as they keep the position at the rear.