Obsessed (2009)

Director: Steve Shill
Genre: Drama | Thriller
Tagline: All's fair when love is war.
Starring: Beyonce Knowles, Idris Elba, Ali Larter, Jerry O'Connell, Christine Lahti

Plot: A successful asset manager, who has just received a huge promotion, is blissfully happy in his career and in his marriage. But a temp worker starts stalking him, all the things he's worked so hard for are placed in jeopardy.

http://www.imdb.com/title/tt1198138/
http://en.wikipedia.org/wiki/Obsessed_(2009_film)