According to WENN:

Actor JOSH HARTNETT has been admitted to a hospital in Los Angeles, California after suffering abdominal pains in the early hours of Monday (30Mar09) morning.  The Black Hawk Down star, 30, was enjoying a night out at the famed Chateau Marmont hotel in West Hollywood when he was struck down with the mystery illness, prompting a pal to make an emergency call for an ambulance at 12.53am, according to TMZ.com.  Hartnett was taken to Cedars-Sinai hospital at around 2am but did not require the use of a stretcher.  A spokesperson for Hartnett was unavailable for comment as WENN went to press.