Back in August Molycorp did a notes and common follow-on offering and MS dropped their coverage in anticipation of bookrunning the stock part of the offering. The stock was at $16.62 on Aug. 1.
It is trading at $6.91 today. If I remember correctly the original Overweight was back in March in the $20's.
UPDATE: Morgan Stanley Downgrades Molycorp Citing Near-term Uncertainty, Removes PT