07/10/1995 at 01:00 AM EDT
LAST SEPTEMBER, WHEN DIANDRA Douglas threw a surprise 50th-birthday party for husband Michael in Manhattan, the Oscar-winning actor rose to toast his wife. "I'm more in love with Diandra now," he proclaimed, "than on the day I married her."
Last week that love scene needed a serious rewrite after Diandra Douglas, 37, filed a petition for divorce from her husband of 18 years. Citing irreconcilable differences, Douglas asked a Santa Barbara court for joint custody of the couple's 15-year-old son, Cameron, and for a share of their property holdings, including homes in Santa Barbara, Aspen, Manhattan and Majorca, Spain.
The pair met at a Washington party in 1977. Michael, then 32, had just won an Oscar for producing One Flew over the Cuckoo's Nest; Diandra, 19, the daughter of an Austrian diplomat, was a sophomore at the Georgetown School of Foreign Service. Nine weeks later they wed.
In recent years the couple separated, and reunited, twice. One source of tension was Douglas's affairs. "The other women," Diandra said last year, "were difficult to deal with." As the couple accumulated homes, they often lived in separate cities, and while Diandra launched a career as a producer of documentaries—including an upcoming TBS series on country music—Michael starred in a string of movies notorious for their sex scenes. He speculated it was playing sexually driven characters in Basic Instinct and Fatal Attraction that had led to rumors he was a sex addict. Douglas denied the charge but admitted that in 1993 he had entered a Tucson rehab center for treatment of substance abuse. No one is sure what led to this latest rift. "In the fall they were talking about having a baby," says a close family friend. "But in the last six months everything fell apart." The couple, Douglas's publicist Allen Burry insists, are still working out their problems. Despite those pending legal papers, Burry said, "they do not plan to divorce."