NEW YORK ( TheStreet) -- CHANGE IN RATINGSAnnTaylor ( ANN) downgraded at Goldman from Buy to Neutral. Estimates also cut, as promotional activity may increase in the women's sector. Aon Corp ( AON) upgraded at BofA/Merrill to Buy from Neutral. Share price drop after the announced acquisition of Hewitt presents buying opportunity, Bank of America/Merrill Lynch said. Maintain $45 price target. Ameristar Casinos ( ASCA) downgraded at BofA/Merrill to Underperform from Neutral as regional gaming revenues have slowed in 2Q10, Bank of America/Merrill Lynch said. Price target sunk to $11 from $20. Calix ( CALX) initiated at BofA/Merrill with an Underperform rating and $10 price target. Street is over optimistic on margins targets. Rockwell Collins ( COL) upgraded at BofA/Merrill to Buy from Neutral. Expecting bizjet recovery and 787 production ramp-up. Maintain $75 price target. Copano Energy ( CPNO) downgraded at UBS from Buy to Neutral. $26 price target. Company will like post weak second quarter results. Commvault Systems ( CVLT) downgraded at Stifel from Buy to Hold. Company is seeing lower sales across the board. Emcor ( EME) upgraded at FBR from Market Perform to Outperform. $39 price target. Company has a strong balance sheet and should benefit from an improving macro environment. FMC Corp ( FMC) initiated at Credit Suisse with an Outperform rating and $73 price target. FMC's significantly improved returns and quality of its portfolio offer a solid balance of growth and cash generation. Hewitt Associates ( HEW) downgraded at Deutsche from Buy to Hold. $48 price target. See limited chance for a competing bid to AON's offer. Illinois Tool Works ( ITW) upgraded at Deutsche from Hold to Buy. $59 price target. Core revenue growth should outperform the sector. JP Morgan ( JPM) rated new Outperform at RBC Capital Markets. $45 price target. Stock has been hit of late, but remains attractively valued, given the normalized earnings potential. Pharmaceutical Product Development ( PPDI) upgraded at Goldman to Buy. $31 price target. Estimates also boosted, given higher sales expectations. Patterson-UTI ( PTEN) upgraded at Morgan Stanley from Equal-weight to Overweight. $22 price target. Company is leveraged to increasing spot rates.