The investigation into Knight Capital stems from last summer, when the firm introduced new trading software.
Trying to stay a step ahead of its competitors, Knight rolled out some new trading software.
The company said the problems happened because of new trading software that had been installed.
Wall Street companies use high-speed trading software to generate billions of dollars in profits.
Trading was suspended on the New York Stock Exchange around 10 10 a.m. after new trading software malfunctioned, exchange officials said.
Eminem's creative partner, the rapper and producer Dr. Dre, sued Napster, the file-trading software company, in 2000.
The Securities and Exchange Commission accused two former executives of AremisSoft, a publicly traded software company, of defrauding investors of at least $200 million.
Efraim F. Gildor, who made a fortune developing financial trading software, and his wife, Catherine W., of Greenwich, Conn., gave $65,000.
Mr. Thompson is the chairman and chief executive of the QueryObject Systems Corporation, a publicly traded software company in Roslyn Heights.
She said she would push ahead with recently proposed rules that would add testing requirements and safeguards for trading software.
A day earlier, the trading software used by the National Stock Exchange stopped functioning properly for nearly an hour, forcing other exchanges to divert trades around it.
