Since Wednesday, the Oscar-winning actress has been staying at the house she bought before her marriage to reality television personality Jesse James five years ago, the celebrity Web site said.
Bullock, who has not spoken publicly about her marital woes, reportedly has seldom left her residence, which is being staked out by paparazzi.
Bullock won the best actress Oscar this month for her work in the feel-good, football-themed family movie "The Blind Side."
Shortly after she collected her statuette, a magazine reported James has been having an 11-month affair with a tattoo model. Several other women have since come forward to claim they had sex with him, too, during his marriage.
Bullock subsequently canceled planned appearances at the London and Berlin premieres of "The Blind Side," citing personal reasons.