When I try to connect the DHT11 to the Arduino and I connect the gnd and 5V at the same time the arduino board stops, why?
You're not connecting it correctly?
Just a guess, in the absence of any details.
I suspect you're connecting something backwards - many things will act like a near short circuit if you reverse Vcc and Gnd (this will also trash the part in question almost every time - DHT11's definitely fry instantly if you connect power backwards, I've lost a couple to that). Parts damaged in this way usually fail shorted, or nearly so.
Hi, Can you post a picture of your project so we can see your connections? Are you using the PC USB to power the circuit or a separate supply?
Thanks Tom... :)