Problem p5000etch SNF 2010-03-17 21:53:14: Ch. B high He leak rates

Tried running several of my wafers into Ch. B several times after one wafer came out burnt due to a 8.6sccm He leak rate (which is below the alarm setpoint of 10?). Same wafers were sometimes leaking < 1sccm and otherwise leaking in the 8.6-8.8sccm range from load to load into the chamber. (I aborted etch steps before they started.) These wafers have clean backsides. Also seems like wafers were emerging from the chamber on the blade rotated somewhat CCW (looking down at the wafer).