This week saw Lehman Brothers replace two of its top executives: CFO Erin Callan and COO Joseph Gregor. The two will remain at the bank in lesser roles.

“As recently as a month ago,” says Justice Litle in Taipan Daily, “Erin Callan was on top of the world.”

The WSJ did a glowing piece on her rise through the ranks. Condé Nast’s Portfolio magazine dubbed her the most powerful woman on Wall Street.

Investors are rushing back into stocks, reports AP, causing the Dow Jones industrials to surge more than 300 points on the first day of the second fiscal quarter.

Financial stocks were among the big winners after Lehman Brothers Holdings Inc. and Switzerland’s UBS AG issued new stock to help bolster their balance sheets. With that upbeat news and a fresh quarter ahead of them, investors appear quite willing to make some bets that the worst of the damage from the nation’s credit struggles has been felt. Moreover, the moves buttressed the view that financial services companies are taking aggressive action to improve their capital bases and stave off the potential of a collapse similar to Bear Stearns Cos. Analysts believe there…