CFO Erin Callan has been the public face for Lehman Brothers ( LEH) over the past six months, trying to convince shareholders that all is well with the smallest of the big investment banks. She failed, and that's why she got sent back to the firm's Investment Banking group this morning and why COO Joseph Gregory got ousted.CEO Richard Fuld has a sterling reputation on Wall Street, and he has seen trouble before and navigated through it. The Long-Term Capital Management imbroglio from 1998 has been often cited as the last example of Lehman fighting off predictions of its demise. Fuld was there then and is firmly in command now. However, after what he allowed to transpire, particularly between Callan and hedge-fund manager David Einhorn over the past several weeks, he needs to be put under the spotlight now.