Lawrie became CEO just last May but Siebel's board of directors and Lawrie "agreed mutually" that he would resign, a company statement said.
Lawrie's dismissal comes just hours before a scheduled meeting of disgruntled institutional shareholders. Providence Capital arranged the New York meeting, at which it planned to discuss with other major investors Siebel's strategy and board of directors composition.
Shaheen, 60, has been a member of Siebel's board since 1995, and was CEO and board chairman of Webvan, a company he joined in 1999 after leaving his job as managing partner and CEO of Andersen Consulting.
Siebel highlighted Shaheen's experience at Andersen Consulting as particularly relevant to his new position at Siebel, saying that he has a track record of building strong customer value and developing a global brand, all while consistently meeting or exceeding financial expectations.
Siebel has been weathering rough financial waters recently. Earlier this month, the company announced that it expects revenue and earnings for the first three months of 2005 to come in below expectations, as a result of deals slipping through in the quarter's final days.
Shaheen said he plans to develop Siebel's strategy on promoting its CRM applications while also extending the reach of its products.
Additional reporting by Marc Ferranti and Stacy Cowley in New York.