ERROR:db.connection_pool:Connection to the database failed

i have installed GTK client and server successfully........but when i run the client using openerp-client the following error occurs at the server side.........
can anyone please help me

[2012-01-03 14:53:03,446][template1] ERROR:db.connection_pool:Connection to the database failed
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/openerp-server/sql_db.py", line 303, in borrow
    result = psycopg2.connect(dsn=dsn, connection_factory=PsycoConnection)
  File "/usr/local/lib/python2.7/site-packages/psycopg2/__init__.py", line 179, in connect
    connection_factory=connection_factory, async=async)
OperationalError: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?