NEW YORK (TheStreet) -- RATINGS CHANGES

Biogen Idec (BIIB) - Get Report was downgraded to hold from buy at Stifel. Valuation call, as some potential risks loom on the horizon, Stiefel said.

CatchMark Timber Trust (CTT) - Get Report was upgraded to hold at TheStreet Ratings. You can view the full analysis from the report here: CTT Ratings Report.

Darden Restaurants (DRI) - Get Report was upgraded at Telsey Advisory to market perform from outperform. Twelve-month price target is $77. Estimates were also increased as the company is cutting costs, Telsey Advisory said.

Nvidia (NVDA) - Get Report was downgraded at Goldman Sachs to sell from neutral. Twelve-month price target is $20. Company is seeing slower core demand and faces a licensing risk, Goldman Sachs said.

Carnival (CCL) - Get Report was downgraded at Deutsche Bank to hold from buy. Twelve-month price target is $51. Company is facing material currency risks, Deutsche Bank said.

EMC (EMC) was downgraded at Piper Jaffray to neutral from overweight. Twelve-month price target is $27. Company is facing increased competition, Piper Jaffray said.

NetApp (NTAP) - Get Report was downgraded at Piper Jaffray to neutral from overweight. Twelve-month price target is $36. Estimates were also cut, as the company is facing increased competition, Piper Jaffray said.

Unit (UNT) - Get Report was downgraded to sell at TheStreet Ratings. You can view the full analysis from the report here: UNT Ratings Report.

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This article was written by a staff member of TheStreet.