NEW YORK ( TheStreet) -- CHANGE IN RATINGSAcorda ( ACOR) downgraded at JP Morgan from Overweight to Neutral, JP Morgan said. $30 price target. Company has limited upside earnings potential. Altera ( ALTR) downgraded at ThinkEquity from Buy to Hold, ThinkEquity said. Valuation call, based on a $40 price target. Amgen ( AMGN) downgraded at JP Morgan from Overweight to Neutral, JP Morgan said. Stock is up 25% in the past two months. $75 price target. Bristow ( BRS) rated new Buy at Dahlman. $54 price target. Company is less cyclical than its peers. Comerica ( CMA) upgraded to buy at TheStreet Ratings. Continental Resources ( CLR) downgraded at Jefferies to Hold from Buy, Jefferies said. Adjustments based on lower 2012 and long-term natural gas price deck. Concur Technologies ( CNQR) downgraded at FBR from Outperform to Market Perform, FBR Capital Markets said. Valuation call, based on a $52 price target. ConocoPhillips ( COP) downgraded at UBS to Sell from Neutral, UBS said. $60 price target. Spin off highlights aggressive upstream valuation. Forest Oil ( FST) downgraded at Jefferies to Hold from Buy, Jefferies said. $13 price target. Adjustments based on lower 2012 and long-term natural gas price deck. Janus Capital ( JNS) upgraded at JP Morgan to Neutral, JP Morgan said. Company is leveraged to better equity returns. McMoran Exploration ( MMR) downgraded at JP Morgan to Underweight, JP Morgan said. Davy Jones well results could prove disappointing. Procter & Gamble ( PG) downgraded at Stifel from Buy to Hold, Stifel Nicolaus said. Valuation call. Research in Motion ( RIMM) upgraded at Deutsche from Sell to Hold, Deutsche Bank said. $18 price target. New management's strategy will be key to survival. Sirius XM Radio ( SIRI) downgraded at Morgan Stanley to Equal-weight, Morgan Stanley said. $2.30 price target. Stock is up 15% since pre-announcement and 2012 expectations may prove optimistic. Salix Pharmaceuticals ( SLXP) downgraded at JMP from Outperform to Market Perform, JMP Securities said. Valuation call, as the stock is already pricing in a lot of good news. Suntrust Banks ( STI) downgraded at BofA/Merrill from Neutral to Underperform, Bank of America/Merrill Lynch said. Earnings recovery will likely take longer than 12 months. $19 price target. Viropharma ( VPHM) downgraded at JP Morgan from Overweight to Neutral, JP Morgan said. Valuation call, based on a $35 price target. Stock is up 69% since October.