By Scott Moritz

U.S. regulators on Monday charged Dallas Maverick owner and outspoken blogger Mark Cuban with using confidential information in 2004 to sell his stake in Mamma.com, a Montreal search engine now known as Copernic (CNIC). His sale of all 600,000 shares helped Cuban avoid a 10% dive in the stock, or about $750,000 in losses, the government contends.

The Securities and Exchange Commission filed a civil lawsuit against Cuban on Monday. No criminal charges were filed.

Cuban, the biggest shareholder in Mamma.com, was allegedly angered by plans for a private sale of discounted Mamma.com stock, according to the lawsuit filed in U.S. District Court for the Northern District of Texas.

Mamma's CEO had contacted Cuban to see if he was interested in participating in the so-called PIPE, or private investment in public equity, according to the SEC complaint. Selling the stock at a discount effectively dilutes the stakes held by existing shareholders. Cuban allegedly responded: "Well, now I'm screwed. I can't sell," according to information provided by the Mamma CEO to regulators.

But sell he did, according to the SEC. One minute after hearing the full details of the private investment offer for Mamma.com shares, Cuban allegedly called his Dallas broker and said: "Sell what you can tonight and just get me out the next day."

The SEC wants Cuban to pay back the $750,000 he avoided in losses after Mamma.com's shares fell as well as a potential fine of $2.25 million.

Cuban issued a statement Monday saying the charges had no merit. "The government's claims are false and they will be proven to be so," he said.

Cuban's net worth has been estimated to be $2.8 billion. His big jackpot came in 1999 when he sold Broadcast.com to Yahoo (YHOO) for nearly $6 billion, one of the largest cash-outs of the Internet boom.

As the owner of the Mavericks and Internet soapbox Blog Maverick, Cuban has displayed a fiery temperament at times. After a few shouting matches with Mavericks head coach Avery Johnson earlier this year, Cuban fired Johnson, the most successful coach in franchise history, at the end of the NBA season in April.

If skirting securities laws to avoid losing a relatively insignificant amount of money sounds strange, it isn't, says Scott Friestad, deputy director of enforcement for the SEC.

"It's not uncommon that the amount of the transaction is not correlated to a person's financial wherewithal," said Friestad. "We've seen sales worth $15,000 by people with $1 million-a-year salaries."