This is a surely a week Goldman Sachs Group, Inc. would like to forget, and not just because several of its top executives were forced to spend hours enduring blistering questions from a Senate committee and listening as profane internal company e-mails were read back in front of a national TV audience.

Goldman bankers awoke Friday to confront two new headaches. The first was the news — which actually broke late Thursday in various publications, including The New York Times and The Wall Street Journal — that federal prosecutors in Manhattan have opened a criminal investigation into Goldman’s trading.