Aflac ( AFL) downgraded at Citigroup from Hold to Sell. $55 price target. Market may be too early anticipating a turnaround in Japanese sales. Altera ( ALTR) upgraded at Citigroup from Hold to Buy. $25 price target. Stock has pulled back sharply since the recent earnings call, and the company is still expected to deliver 8% earnings growth in 2008. Acuity Brands ( AYI) upgraded at CIBC from Sector Perform to Outperform. $45 price target, following the ZEP spin-off. Valuation call, as the company could continue to expand margins in the new year. Chattem ( CHTT) upgraded at Wachovia from Market Perform to Outperform. Pullback over the past two weeks has created an attractive buying opportunity. Company can post 20% earnings growth in 2008. Concur Tech ( CNQR) downgraded at Merrill from Neutral to Sell. Expect more risk to 2008 estimates, if the US economy continues to slow. Echostar ( DISH) downgraded at Citigroup from Buy to Hold. $52 price target. Sub-prime concerns could lead to a higher churn rate. Estimates also cut. Dover ( DOV) downgraded at Merrill from Buy to Neutral. Tech business seems to have stabilized, but the company's other divisions could suffer from a slower US economy. Energy Conversion ( ENER) downgraded at UBS to Neutral rating from Buy. Price target drops to $33 from $43 and FY 2008 eps estimates slashed to $(0.01) from $0.30.