Sprint Nextel (NYSE: S) chairman and CEO Gary Forsee is stepping down effective immediately amid investor and board unrest. Forsee’s departure comes less than a week after back-to-back reports from the Wall Street Journal that a major investor was planning a proxy fight and that the Sprint Nextel board has been looking for Forsee’s successor since August. Forsee became CEO of Sprint in 2003 and led the company into a merger with Nextel.

From the release: James Hance, Jr., a member of the board, has been appointed acting non-executive chairman while CFO Paul Saleh, a Nextel vet, will serve as acting CEO until a successor is found, A committee of the board will conduct the search, which will focus on outside candidates. Director Irvine Hockaday said the board thought the time was right for new leadership.

Sprint Nextel also released preliminary results for its 3Q07 earnings that illustrate some of the reasons behind the moves: the company expects to report a net loss of approximately 337,000 post-paid subscribers in the third quarter. Also, operating revenue for the year is going to coming in “slightly below” previous guidance.

More to come.

• Sprint Board Starts Search For CEO Forsee’s Successor: Report
• Sprint Threatened With Proxy Vote Over Leadership