Some people just don't learn!

Josh Hartnett was hospitalized last week with a little stomach problem (you know, when Sienna Miller rushed to his side?) and now the actor is doing the exact same thing that got him into trouble the first time - partying!

According to an inside source, Hartnett knocked back a couple drinks at the Chateau Marmont last night, just days after being released from Cedars-Sinai...

Is he really up to his old tricks so soon? Be careful, dude!