The former CFO of Aetna, Alan Bennett, has come out of retirement to head up H&R Block as interim CEO. He retired from Aetna earlier this year.

Richard Breeden, a former Securities and Exchange Commission chairman who recently led a successful proxy fight with H&R Block, was elected chairman. Bennett and Breeden replace Mark Ernst, who resigned as chairman, president, and CEO.

Bennett was Aetna’s CFO for six years. Before that he served as the company’s controller and head of internal audit. He currently is a director and audit committee chairman of Halliburton Co. and also is a director of The TJX Companies.

Breeden joined H&R Block’s board in September 2007 after his $1 billion hedge fund won a showdown at the company’s annual meeting. He served as SEC chairman 1989 to 1993. Since 1996 he has led his own firm that has advised companies and boards on capital-markets issues, financial restructurings, and corporate governance.

When Bennett announced in April 2006 that he planned to retire from Aetna, the company’s stock price fell by more than 21 percent in a single day. That same day the company also announced higher-than-expected medical costs, which also likely contributed to the selloff.