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 her TV personality husband, Jesse James, has been having an 11-month affair with a tattoo model.
Bullock has not been seen in public since the news broke last week, and she is reported to have moved out of the home she shared with James.
She canceled planned appearances at the London and Berlin premieres of "The Blind Side," citing personal reasons, as well.
TMZ cited unnamed sources Tuesday as saying Bullock's representatives have been consulting divorce attorneys.
The entertainment news Web site also said while James doesn't plan to initiate divorce proceedings, his camp is talking to lawyers to see who might be interested in representing him if Bullock files.
Asked if a divorce petition is expected, one insider told TMZ, "Something's happening."
However, Bullock's representatives denied the online report.
"Neither she nor her representatives have contacted or shopped around for divorce lawyers," said a statement issued to People.com.
James's spokesman also said the TMZ report was untrue, People.com said.