Finally solved the mystery -

"We have concluded the most likely cause of this anomaly is due to high friction, which was caused by the loss of lubrication in the joint when it flew," Suffredini said. "The way we lubricate that joint is we put a gold plating on the (TBA) rollers. This is a very soft material and over time, it kind of wears off the roller and finds its way onto the race and fills in the very small, microscopic holes and provides, basically, a lubricant that will wear over time. But it was intended to wear very slowly over time...We have proven through testing that once you take the lubrication off this joint, it will damage the race very, very quickly."

"We will take that opportunity to clean up that race and then we'll also lubricate that race. What we're doing here is we're trying to modify the system just enough so that when we do have to rotate it, we minimize both the vibrations associated with the damage to the race and the contamination that's currently on the race, that helps us with structural life. In addition to that we want to reduce the amount of current required to drive this joint to make sure we never reach the maximum current the motor can drive to. So that's what these two steps do."

As a precaution, the astronauts also plan to lubricate the port-side SARJ."

A great article in <a href="http://spaceflightnow.com/shuttle/sts126/080925sarj/>Spaceflight Now

Enjoy, Vince