Reset postgres password v9.1
Try to run psql -h 127.0.0.1 (...) 

When you use the -h that will tell psql to use a TCP/IP connection
('h' is from host), and the parameter after -h is the name of the host.

In that case 127.0.0.1 is a default address, meaning localhost.

If you don't use the -h (with host next to this parameters) it will
use a "local way" of connection called unix domain sockets.