Before the close of trading on 21-Jan-09, the Wall Street Journal reported (using an anonymous source) that the SEC had opened an investigation into how Apple had disclosed information related to Steve Jobs's health. Jobs, currently on leave from the company except for major strategic decisions until June 2009, has made a number of brief statements about his health over the last several months. (See "Steve Jobs Takes Medical Leave Until June," 01-14-2009.)
Publicly traded companies are required to disclose matters that have a material effect on a company's performance, which could include a CEO who was unable to perform as expected. The SEC typically only discloses their investigations when a settlement is made, fines imposed, or prosecution intended.