ACI, IBT, Illinois Tool, National Oilwell: U.S. Equity Movers

The following is a list of companies whose shares are having unusual price changes in U.S. exchanges. Stock symbols are in parentheses after company names and prices are as of 10:10 a.m. in New York.

ACI Worldwide Inc. (ACIW) fell the most since February 2003, dropping $5.21, or 22 percent, to $18.30. The maker of software for electronic payments reported lower fourth-quarter sales than analysts estimated and said it's reviewing some tax deductions.

Ambac Financial Group Inc. (AMBC) soared $4.29, or 19 percent, to $27.10 for the biggest jump since its July 1991 initial public offering. MBIA Inc. (MBI) added 2.7 percent to $28.34. Moody's Investors Service affirmed the AAA credit ratings on the companies' insurance subsidiaries.

American Dairy Inc. (ADY US) dropped $1.91, or 14 percent, to $12.09. The milk producer may continue to drop as the company faces a U.S. Securities and Exchange Commission probe of its Hong Kong-based auditor, Barron's reported.

Apria Healthcare Group Inc. (AHG US) rose $1.43, or 6.2 percent, to $24.53, the highest since Oct. 15. The provider of home health-care products and services was boosted to ``neutral'' from ``sell'' by UBS AG.

Berkshire Hathaway Inc. (BRK/A) (BRK/A US) had the biggest drop since March 2005, losing $5,600, or 3.9 percent, to $137,400. The insurer controlled by billionaire Warren Buffett may be overpriced by about 12 percent at $143,000, Barron's reported, citing Credit Suisse Group analyst Charles Gates who puts the 12-month share price estimate at $125,000. Berkshire rose $600 to $143,000 on Dec. 14.

Grant Prideco Inc. (GRP US) climbed the most since November 2001, rising $7.29, or 15 percent, to $54.75. National Oilwell Varco Inc. (NOV) , the largest U.S. maker of oilfield equipment, agreed to buy Grant Prideco for about $7.4 billion to add sales of drilling pipes and bits. National Oilwell slipped 6.2 percent to $72.60.

IBT Bancorp Inc. (IRW US) jumped the most since June 1994, climbing $8.63, or 45 percent, to $27.82. The holding company for Irwin Bank & Trust Company of Pennsylvania agreed to be bought by S&T Bancorp Inc. (STBA) for about $171 million.

Illinois Tool Works Inc. (ITW) fell the most since July 2004, dropping $2.92, or 5.2 percent, to $52.98. The maker of Duo-Fast nail guns and Wilsonart countertops cut its full-year earnings forecast as lower-than-expected sales in North America and acquisitions hurt profit.

KongZhong Corp. (KONG) American depositary receipts (KONG US) advanced the most since Sept. 27, jumping $1.03, or 19 percent, to $6.45. The company, which sells ringtones and games to mobile-phone users in China, said it expects revenue of as much as $19.5 million in the fourth quarter. That beat the average estimate of $17.4 million by analysts in a Bloomberg survey.

LDK Solar Company Ltd. ADRs (LDK US) rallied $15.63, or 28 percent, to $72.47, the highest since Sept. 26. The Chinese maker of silicon wafers used in solar cells said a probe by the company's audit committee found no ``material errors'' in its reported silicon inventories.

Legg Mason Inc. (LM) lost $1.87, or 2.6 percent, to $71.41, the lowest since Nov. 27. The money manager's debt outlook was lowered to ``negative'' from ``stable'' by Moody's Investors Service, in part because of possible losses from structured investment vehicles in its money-market funds.

Savient Pharmaceuticals Inc. (SVNT US) rose $2.15, or 11 percent, to $21.05, the highest since November 1986. The developer of a treatment for severe gout was lifted to ``buy'' from ``neutral'' by Merrill Lynch & Co.

SLM Corp. (SLM) gained the most since Nov. 23, adding 92 cents, or 3.5 percent, to $27.61. The company named Executive Chairman Albert L. Lord its chief executive officer, returning him to a role he held with the student-loan company for eight years.

Trane Inc. (TT US) surged $8.78, or 24 percent, to $45.98 for the biggest gain in the Standard & Poor's 500 Index. Ingersoll-Rand Co. (IR) , the maker of Thermo King truck refrigerators, agreed to buy Trane for $10.1 billion in cash and stock to gain air-conditioning and heating systems. Ingersoll-Rand declined 5.9 percent to $46.29.

To contact the reporter on this story: Lu Wang in New York at lwang8@bloomberg.net

To contact the editor responsible for this story: Chris Nagi at chrisnagi@bloomberg.net.

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