"Improper Channels," now at area theaters, mounts a mildly amusing assault on presumptuous bureaucrats. A spruced-up and calmed-down Alan Arkin is teamed rather attractively with Mariette Hartley, a potentially wonderful resource wasted systematically by movie producers for the past 20 years. They play a politely estranged professional couple -- he's an architect and she's an author -- who reconcile in the face of highhanded treatment by busybody social workers. While riding with her father, the couple's 5-year-old daughter (Sarah Stevens) suffers a slight bump on the head when he stops suddenly for a reckless driver. Arkin rushes her to the hospital, where's she treated by a competent doctor but willfully misunderstood by an incompetent social services officer (Monica Parker), who jumps to the conclusion that a case of child abuse has come to her overeager attention. Taking outrageous liberties with the facts of the case, her own authority and the lives of the people involved, she proceeds to transfer the child to an orphanage and wind the parents in a tangle of red tape, provoking them into retaliatory sabotage -- a scheme to scramble all the records kept in the welfare department's central computer.

The screenwriters -- Morrie Ruvinsky, Ian Sutherland and Adam Arkin -- depict welfare bureaucrats in Toronto as a notorious nest of sneaks and buttinskis. The prejudicial setup is softened to some extent by the skill of Parker and Harry Ditson, who plays her peevish, devious superior. They embody presumptuous behavior with considerable comic originality and finesse, so the villains acquire some dimension as antagonists and provide reliable incidental amusement.

If memory serves, Arkin is usually better served by comic roles that ask him to appear more or less serious and thoughtful rather than impulsively clownish. "Improper Channels" asks for his relatively subdued but vastly more appealing side. Within the limits allowed by absurd twists of plot, he and Hartley also generate a persuasive feeling of marital familiarity and affection. In a less random era of popular filmmaking Hartley might have been developed by an appreciative, astute management into an image of the sane, humorous, desirable married woman as appealing as the image Myrna Loy embodied for an earlier generation. It still might happen, I suppose, especially if the networks ever get around to pairing her and James Garner in a hit series, say an update of "Mr. & Mrs. North." There's one scene in "Improper Channels" that also suggests Hartley possesses an untapped comic talent for flying off the handle: Arkin trying to hold her back while she tries to do bodily harm to Ditson and shouts, hyperbolically of course, "I'm coming back here with a bazooka to blow your brains out! There'll be brains all over the floor!"

The Canadian director, Eric Till, has a spotty record and modest skills, but "Improper Channels" remains tolerable and proficient as long as it doesn't overreach for yucks. "Hot Millions," an earlier Till credit, which also exploited the idea of using a computer for unauthorized purposes, showed a similar agreeable touch with low-key, unassuming character comedy. While never more than half-good, if you enter with few expectations "Improper Channels" shouldn't seem half-bad.