pymssql Connection to the database failed for an unknown reason

Hello
I am using pymssql to connect to MSSQL2008 database. But an error
occurs:
------------------------------------------------------------------
>>> import pymssql
>>> conn = pymssql.connect(host='orgilhpnb\mssql2008', user='erp', password='123', database='eoffice_clone')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/pymodules/python2.6/pymssql.py", line 609, in connect
raise InterfaceError, e[0]
pymssql.InterfaceError: Connection to the database failed for an
unknown reason.
------------------------------------------------------------------

The host name, user, password and database name are all correct.
Why I get an error? Please help me!

Any suggestion would be highly appreciated!

Best regards,
Orgil