Casey's General Stores ( CASY) downgraded at FBR to a Market Perform rating as upside to target price from here is just 10%. First Marblehead ( FMD) downgraded at FBR to an Underperform rating as analysis of trust performance suggests increasing risks that loan losses may not be sufficient. Target price is now $26. Grant Prideco ( GRP) upgraded at UBS to Buy rating from Neutral. Price target lifts to $65 from $62 and FY 2008 eps estimates upped to $4.65 from $4.55. Intersil ( ISIL) downgraded at Jefferies to Hold rating from Buy. Price target slashed to $30 from $38 and FY 2008 eps estimates dip to $1.59 from $1.69. Sierra Pacific Resources ( SRP) downgraded at Deutsche Bank to a Hold rating as rate base upside is too opaque. Target price is $18.50. Tidewater ( TDW) upgraded at Jefferies to Buy rating from Hold. Price target and FY 2008 eps estimates remain at $66 and $6.31, respectively.