Lehman Brothers Gives Executives the Boot

Investors fear that Lehman's troubles could make it the next Bear Stearns, which in March, on the verge of bankruptcy after rumors about its liquidity hammered the stock, sold itself to JPMorgan Chase(JPM Quote). Bear shareholders approved the deal last month.

Callan's fall is precipitous. The CFO was widely lauded for her stewardship of the firm earlier this year, when it was regarded as one of the few Wall Street firms to navigate the credit crisis relatively unscathed. But recently, she was assailed by hedge fund manager David Einhorn of Greenlight Capital for masking losses.

Callan and Gregory's departure are the latest in a growing line of executive casualties amid the credit crunch.

Cramer: Lehman Not Out of the Woods

Ex-Merrill Lynch(MER Quote) CEO Stanley O'Neal and former Citigroup(C Quote) head Charles Prince were among the first high-profile casualties late last year, after their banks posted big losses tied to the deteriorating mortgage market.

Ex-Bear Stearns CEO James Cayne gave up the job in January, but retained the chairman title before the firm sold to JPMorgan.