June Haver, 79, the sunny film actress of 1940s musicals who was promoted as "Hollywood's sweetest star" but whose personal turmoil caused her to flee briefly to a convent in Kansas, died of respiratory failure July 4 at her home in Brentwood, Calif.

Performing since 6, Ms. Haver amassed a range of early accomplishments, including oratory, singing and piano competitions (once under the baton of Eugene Goossens). She was a professional big-band singer while still a teenager and won a contract with Twentieth Century Fox, which wanted a lookalike successor to the popular Betty Grable.

Ms. Haver became an overnight leading lady. Her roles in films such as "Irish Eyes Are Smiling" (1944) with singer Dick Haymes and "Three Little Girls in Blue" (1945) with Vivian Blaine and Vera-Ellen showcased a charming but limited range vastly aided by her remarkable beauty. One notable achievement was having introduced the jazz standard "Give Me the Simple Life" in the musical "Wake Up and Dream" (1946).

Most of the films were of fleeting impression, and her career had dwindled by the early 1950s. She also endured tragedies in her private life. She had divorced the jazz trumpeter and late-night carouser Jimmy Zito -- she described the marriage as "the biggest mistake of my life" -- and several other romances had gone nowhere. Her subsequent engagement to a handsome Hollywood dentist named John Durzik ended with his death from hemophilia during routine surgery.

In 1953, Ms. Haver, an increasingly devout Catholic, left her $3,500-per-week contract and joined the Order of the Sisters of Charity in Leavenworth, Kan.

Suffering from migraine headaches, she soon found the order's rigors overwhelming and returned to Hollywood.

At a New Year's Eve party, she met actor Fred MacMurray, 17 years her senior and recent widowed. "I proposed to him," she said, and they lived quietly on a ranch until he was offered the leading role in the long-running television program "My Three Sons."

The marriage lasted until MacMurray's death in 1991 and was, by many accounts, a key component in her indefatigably upbeat disposition. Her friends were keen on telling her, "Cheer down, June."

Ms. Haver was born Beverly Jean Stovenour in Rock Island, Ill., on June 10, 1926. Her mother, a former actress, encouraged her interest in entertaining. Ms. Haver's parents divorced, and she took her acting surname from her stepfather.

"At 11," she later said, "I dreamed up a juvenile program, emceed it, sang on it, played the piano and sold the idea to a local ice cream company, which became my paying sponsor." She was paid $2 a week.

She also sang with bandleaders who came to town, including Ted Fio Rito, who brought her and her mother to Hollywood. There, she finished her schooling, appeared in two musical film shorts and played a hatcheck girl in the Alice Faye musical "The Gang's All Here" (1943).

At Fox, Darryl F. Zanuck became her chief backer, hoping her middle-America looks would find mass appeal. She had leading roles in 14 films, and her leading men included MacMurray ("Where Do We Go From Here?"), Ray Bolger ("Look for the Silver Lining," in which she played stage star Marilyn Miller, one of her best parts) and Dan Dailey ("The Girl Next Door," her final film).

After marrying MacMurray, Ms. Haver turned down film and television parts, saying said she wanted to retire "while I was still under rather than over the hill."

Survivors include two stepchildren; two adopted daughters; seven grandchildren; and four great-grandchildren.

June Haver on the cover of a fan magazine. She starred in films such as "Irish Eyes Are Smiling" and "Three Little Girls in Blue."