People magazine reports that, just eight days after taking home the Oscar for her hit movie, "The Blind Side," Bullock moved out of the Los Angeles home she shared with her husband of five years, reality TV star Jesse James.
Bullock and James -- who looked like a very close and happy couple at the awards ceremony -- were married in July 2005.
But In Touch magazine reports that, while Bullock was filming "Blind Side" in Atlanta, James was with tattoo model Michelle "Bombshell" McGee in L.A.
McGee, a mother of two, told In Touch, "I would never have hooked up with him if I thought he was a married man. He gave me the impression they were separated."
She even claimed to have a pet name for James - "Vanilla Gorilla" - because of his physical gifts.
On Wednesday, Bullock pulled out of the London "Blind Side" premiere, saying in a statement, "Due to unforeseen personal reasons, a trip abroad to support "The Blind Side" has been deemed impossible at this time."
Bullock and James have been involved in a long custody battle with James' ex-wife, former porn star Janine Lindemulder.
If the supposed split becomes permanent, Bullock would join a long list of actresses struck by what's called the "Oscar curse" -- relationships that have broken up shortly after winning Best Actress honors.
Among them: Hilary Swank, Halle Berry, Reese Witherspoon, Julia Roberts and Kate Winslet.