Two days after one of his employees mistakenly approved a $900 million payment to a group of Revlon Inc. lenders, Citigroup Inc. executive Vincent Farrell was looking to report some good news about the bank’s recovery effort. “Quick update, just crossed the 100MM mark,” Farrell, head of North American loan operations, said in an instant message to his boss. “Good,” Brendan Zeigon, who oversees global loan operations and credit risk management services, messaged back. “I would love to get to 200.” The two were in a fix. An executive was “on a war path” over the error -- one of the biggest in the industry in recent memory -- which happened as Citigroup was trying to make a periodic interest payment. Instead the bank wound up sending the creditors the full amount they were owed, more than 100 times what it intended to distribute. And, as administrative agent on the loan, it had come out of its own pocket.