SEC charges that Dallas Mavericks owner Mark Cuban engaged in insider trading, allegedly using confidential information on a stock sale to avoid more than $750,000 in losses, could strike him out of the running to buy Tribune's Chicago Cubs . The SEC's lawsuit alleges that in June 2004, Mr. Cuban was invited to participate in a stock offering by search engine Mamma.- com, the terms of which he agreed to keep private. The SEC says Mr. Cuban knew the shares would be sold below their market price and, a few hours after receiving the information, told his broker to sell all shares in the company. On his blog, Mr. Cuban called the government's claims ``false'' and vowed to fight them. The accusation could hurt his chances as bids for the Cubs approach a Nov. 26 deadline, some observers say. Mr. Cuban is one of five bidders.