borrowed a friends Duemilanove and tried the same hookup
same result
most recent library I tested is from ADAfruit at GitHub - adafruit/DHT-sensor-library: Arduino library for DHT11, DHT22, etc Temperature & Humidity Sensors
though I added at line 33
Serial.print("h = ");
Serial.println(h);
Serial.print("t = ");
Serial.println(t);
which spits out the result of
DHTxx test!
Read failh = 0.00
t = 0.00
Failed to read from DHT
h = 0.00
t = 0.00
Humidity: 0.00 % Temperature: 0.00 *C
h = 0.00
t = 0.00
same result with 3 different DHT11 sensors
this one is starting to really bug me
** EDIT: added debugging code & result **