Now that Sandra Bullock has stepped away from writer-director Ben Younger's "Prime," Uma Thurman has risen to the top of the list of possible replacements for the project, which is set to begin filming Sept. 7. Although no offer has been made yet, Thurman, who most recently starred in the "Kill Bill" movies, is likely to be paged to play a thirtysomething woman who falls for the son (Bryan Greenberg) of her therapist (Meryl Streep). Bullock has signaled that she will not do the film unless script issues are resolved to her approval (HR 8/26). The film is being produced by Team Todd and financed and executive produced by Stratus Films. Universal and Focus are distributing.