The chief of the NASDAQ stock exchange says he is embarrassed and apologizes for the technical problems that led to investor losses on the opening day of trading of Facebook shares.

Robert Greifeld told CNBC television on Wednesday that the problems were a low point for NASDAQ. He said he is focused on the future and working on building a better and stronger organization.

NASDAQ says it will offer $40 million in compensation to traders who lost money because of the Facebook opening day problems. But some investors estimate their losses to be as much as $100 million.

Computer problems delayed trading in Facebook shares on May 18 by about 30 minutes. When the problems were resolved, some traders discovered that they had paid more than the opening price of $38 per share. Others found out they bought more shares than they had ordered.

The technical problems are only part of the controversy surrounding Facebook's initial public offering. The company's main underwriter, Morgan Stanley, has been accused of cutting its forecast of Facebook's future revenues just before the shares went on sale. The financial services firm allegedly told large investors while withholding the information from average investors.

Morgan Stanley says it did nothing wrong.

Facebook closed at $26.81 per share Wednesday, down about 29% from its May 18th opening.