cURL to Bitcoin-Qt on Mac fails
Three things to check : 


Is there rpcssl=1 in your bitcoin.conf ? If so, set it to 0 or make HTTPS connections only
Have you set rpcallowip=127.0.0.1 ?
Try connect to http: //yourname:yourpassword@127.0.0.1:8332/ directly


And the fourth thing to check (as I saw your answer) :


Check if you have correctly entered your username and password ;)