As a longtime fan of Diane Keaton, it's always disheartening to see her in roles that seem inadequate for the Oscar-winning, lean and brainy hipster icon of the 1970s ("Annie Hall," "Manhattan" and "Interiors," to name just a few). But her most recent foray into mainstream rom-com is just plain painful.

Titled "Because I Said So," the film is a blend of the excruciating and exasperating, whose idea of a comedic high point is having Keaton accidentally access a porn site on her home computer with the sound going full blast, and panic while her dog gleefully humps the couch. If there were such a thing as a Cinema Supreme Court, scenes like this would surely be sentenced 20-to-life in a maximum-security prison.

The director is Michael Lehmann, whose debut 1989 work "Heathers" was a darkly observed high-school satire. It seems he spent the past two decades ridding himself of most of the cynicism and edge that made "Heathers" so compelling. "Because I Said So" is a train-wreck of slapstick, sexual innuendo and Diane Keaton screaming out in sexual ecstasy — or just screaming.