Oscar Winner Best Actress in 2009 and 2010 Sandra Bullock and Kate Winslet

They turn heads on the red carpet, are besieged by the world's top designers, give tearful acceptance speeches, and go home with a little gold man called Oscar.

But shortly after many actresses win the movie industry's highest honour, their most important relationships fall apart in what has become known in Hollywood as the "Oscar curse."

Sandra Bullock and Kate Winslet, the 2010 and 2009 best actress Oscar winners, this week joined Halle Berry (2002), Julia Roberts (2001), Reese Witherspoon (2006) and Hilary Swank (2005) on that list.

Bullock's husband of five years, motorcycle enthusiast Jesse James, responded to allegations of cheating on Bullock with an apology on Thursday for the grief he had caused. The reasons behind the separation of Winslet from her film director husband Sam Mendes have so far remained private.

Tom O'Neil of the awards website TheEnvelope.com, pondered the link between such breakups and Oscar glory.

"Is it because victory goes to their heads and these women become impossible divas?," O'Neil wrote in a blog. "Or is it because their men are overly macho types who can't tolerate being upstaged?"

In Bullock's case, In Touch Weekly magazine this week quoted a model in California as saying she slept with James while his wife was in Atlanta last year filming what would be her Oscar-winning role in dramatic movie The Blind Side.

New York divorce lawyer Paul Talbert dismissed the notion of an Oscar curse, saying such breakups were more likely a result of long absences by one partner in a marriage.

"The reality is that these women are extremely successful, hard working women who must spend months away from their families shooting and promoting their films," Talbert said.

"It is no different than the situations of high income New York families where one spouse is often on the road several times per month raising capital for their hedge funds or researching businesses to invest in," he added.

But Hollywood can bring extra temptations in the form of beautiful men and women and the intimacy that can spring from long hours on film sets, especially in romantic scenes. And while nearly 50 percent of marriages fail, it seems the stars have an especially hard time making marriage work.

"Celebrities are uniquely exposed to a lot of very attractive people," said Bonnie Fuller, editor-in-chief of website HollywoodLife.com. "You have to be especially strong to resist that."

Bullock's recent Golden Globe and Screen Actor's Guild acceptance speeches were ironically peppered with heartfelt tribute to James, who despite brief appearances in a number of TV reality shows does not move in A-list circles.

"You get dressed up in monkey suits, and you sit at a table with people you don't know. I love you so much, and you're really hot!," she told him, and the world, in February.

Yet for some men, playing second fiddle in such high profile occasions may be too much to take, said Fuller.

"A lot of guys cannot handle a strong, successful woman, and the Oscar has to be one of ultimate accolades one can receive," she said.