Don’t expect William Mapother to jump up and down on Oprah‘s sofa anytime soon. Interviewed this week on BlogTalkRadio, the “Lost” actor — a k a Tom Cruise‘s cousin — is cagey as to whether he shares the “Mission: Impossible” star’s adherence to the gospel of L. Ron Hubbard. But one thing’s for sure: He has learned from Cruise what not to do. When a caller asked, “Are you now a Scientologist?” Mapother — who made his name playing Marissa Tomei‘s psychopathic ex in the 2001 Oscar-nominated flick “In the Bedroom” — replied: “I have kind of an unusual feeling about questions like that. On the one hand, I’m grateful that people are interested . . . At the same time . . . there’s kind of an ever-wavering boundary between the things I’m willing to talk about, and the things I’m not. And part of the reason that I find myself particularly cautious in this area is because of the things my cousin has been through.”