Bullock married a custom motorcycle manufacturer and reality TV star Jesse James in 2005. In several award ceremonies earlier this year, the actress attributed much of her recent success to her happiness at home. If the claims of infidelity by James prove correct, Bullock will join a long list of actresses whose relationships have fallen apart shortly after they won an Oscar.
Recent previous winners afflicted by what has come to be known in Hollywood as the "Oscar curse" for best actresses include Hilary Swank, Halle Berry, Reese Witherspoon and Julia Roberts.
British actress Kate Winslet, who won the Oscar last year for her role in the "The Reader", announced on Monday that she and her film director husband, Sam Mendes, had separated.