Google ( GOOG) shares shot up in late trading Thursday after Standard & Poor's said it will add the search-engine giant to its S&P 500 index. Google, which has been spurned by the S&P in earlier opportunities for addition to the index, will replace Burlington Resources ( BR) after the close of trading March 31. Google shares jumped $30.97, or 9%, to $372.86 in after-hours trading Thursday.

Shares of Idenix Pharmaceuticals ( IDIX) plummeted in late trading after the company said it had lowered dosing levels in an ongoing clinical trial for the hepatitis C treatment valopicitabine after observing dose-related gastrointestinal side effects in patients. Idenix said the modifications will delay the drug's development, but the company noted that it was encouraged by the level of antiviral activity in the lower-dose arms. Shares fell $4.26, or 21%, to $15.99 in late trading.

Palm ( PALM) shares rose after the gadget maker's fiscal third-quarter results and fourth-quarter guidance beat analysts' estimate. For the quarter ended Feb. 28, the company's earnings rose to $19.8 million, or 19 cents a share, up from $10.6 million, or 10 cents a share, a year earlier. Revenue rose to $388.5 million from $285.3 million. Analysts had forecast earnings of 16 cents a share and $374.7 million in revenue.

For the current quarter, Palm forecast earnings of 22 cents to 23 cents a share, before items, on revenue of $400 million to $405 million. Analysts project earnings of 20 cents a share and revenue of $395 million. Shares advanced $1.17, or 5.8%, to $21.31 after hours.

Synnex ( SNX) shares climbed after the IT supply-chain services company beat Wall Street's first-quarter earnings expectations and offered a solid guidance. Synnex reported earnings of $10.7 million, or 34 cents a share, up from $8.6 million, or 27 cents a share, a year ago. Excluding stock-compensation costs, the company earned $11.2 million, or 36 cents a share. Revenue increased to $1.50 billion from $1.31 billion. Analysts polled by Thomson First Call predicted earnings of 33 cents a share, before items, on revenue of $1.45 billion.

For the second quarter, Synnex sees earnings of 35 cents to 37 cents a share, excluding 2 cents to 3 cents in stock-option expenses. The company targets revenue of $1.45 billion to $1.50 billion. Analysts see earnings of 34 cents a share and revenue of $1.47 billion. Synnex gained $1.08, or 5.8%, to $19.56.

@Road ( ARDI) shares drove higher after the provider of mobile-communications systems said it signed an agreement to provide services to Eaton's ( ETN) vehicle-solutions business unit. Under the terms of the agreement, the two companies will jointly develop systems for truck fleets. The systems will allow fleets to monitor their vehicles, schedule downtime and provide drivers with enhanced safety , Eaton said. @Road shares gained 38 cents, or 8%, to $5.13 in after-hours trading.

Smart Modular Technologies ( SMOD) said its second-quarter net profit fell to $800,000, or 1 cent a share, from $7.8 million, or 15 cents a share, a year earlier. Excluding various items, the electronic-subsystems supplier posted earnings of $8.5 million, or 15 cents a share, up $7.8 million, or 15 cents a share, from a year ago. Analysts expected earnings of 12 cents a share on this basis. Sales fell to $163.7 million from $164.4 million a year ago, but beat Wall Street's target of $159.7 million.

For the third quarter ending in May, Smart Modular forecast earnings of 14 cents to 15 cents a share, before items. The company sees sales of $165 million to $175 million. Analysts, on average, project earnings of 14 cents a share and sales of $168 million. Shares, which closed regular trading up 4%, fell 5.5% in late trading to $8.90.