A top-notch investigative producer from Chicago is suing NBC over alleged ethical lapses involving the news series "To Catch a Predator." Marsha Bartel, who was fired last December after a stellar 21-year career with NBC (including 10 years at WMAQ-Channel 5), claimed she was forced out after blowing the whistle on the show for violating journalistic ethical standards and many of NBC's own policies and guidelines. A copy of her lawsuit, filed in federal court May 24, turned up this week on thesmokinggun.com. Bartel, 49, who now works with news anchor Mark Suppelsa as a special project producer at Fox-owned...