Private drama plagues Oscar winner Sandra Bullock

Sandra Bullock is on a career high. America's Sweetheart and Miss Congeniality was repeatedly anointed as Hollywood royalty this year, sweeping awards season and capping it off with an Oscar for her role as a devoted mom in The Blind Side.

But as this Tinseltown fairy-tale played out on camera, real-life drama may have been brewing behind the scenes.

• Sandra Bullock's husband says sorry after affair rumours

With worldwide attention on the brand-new Oscar winner - who first captured hearts as a brave bus passenger in 1994's Speed and went on to amass more than two dozen movie credits - Bullock is being dogged by tabloid reports of problems with her husband of nearly five years.

Internet rumors surfaced on Wednesday that the 45-year-old actress' husband, celebrity motorcycle builder and reality-TV star Jesse James, had been unfaithful while she was making her Oscar-winning film. Bullock subsequently canceled a planned appearance next week at the London premiere of The Blind Side, citing "unforeseen personal reasons."

On Thursday, James apologised to his wife and three children from previous relationships through a statement issued to People magazine and later obtained by The Associated Press.

"It's because of my poor judgment that I deserve everything bad that is coming my way," he said. "This has caused my wife and kids pain and embarrassment beyond comprehension and I am extremely saddened to have brought this on them."

He added that "the vast majority of the allegations reported are untrue and unfounded," but offered no other details, saying, "Beyond that, I will not dignify these private matters with any further public comment."

Representatives for Bullock did not respond to calls and e-mails seeking comment on Thursday.

Publicly, there was no indication of strife as the couple appeared happily arm-in-arm throughout Hollywood's awards season while Bullock racked up the accolades.

She called her husband "sexy" as she accepted her Screen Actor's Guild award. Backstage, he held her purse as she spoke to reporters.

At the Golden Globes, Bullock told James from the stage, her voice cracking with emotion: "There's no surprise that my work got better when I met you. Because I never knew what it felt like for someone to have my back."

Things were different at the Academy Awards.

Bullock did not thank her husband, who appeared teary-eyed on camera as she accepted her award. Instead she thanked mothers and parents everywhere - including a poignant tribute to her own mother - along with her fellow nominees and "everyone who's shown me kindness when it wasn't fashionable."

Still, Bullock and James, 40, walked hand-in-hand down Oscar's red carpet, celebrated together at the parties afterward and were photographed outside a Long Beach burger joint the next day.

The actress and the Monster Garage star met in 2003 and married in 2005. Initially deemed an odd match by some - she's the girl next door, he's a tattooed bad-boy - the couple stayed blissfully out of the public eye while continuing their individual successes.

Bullock had dated actors, including Matthew McConaughey and Ryan Gosling, and was engaged to Tate Donovan, but her marriage to James is her first. James had been married twice before and is in an ongoing dispute with his most recent ex-wife over custody of their 5-year-old daughter, Sunny.

Bullock has said she loves James' children as though they were her own and that the eldest, Chandler, selected her regal Oscar gown.

While winning an Academy Award can be a boon to actors' careers, it's not always great for their personal lives. Sean Penn won the best-actor Oscar last year for Milk and split with his wife, Robin Wright Penn, a few months later. (He didn't thank her in his speech, either.) Last year's best-actress winner, Kate Winslet, separated from her husband, director Sam Mendes, earlier this week.