[cifs-protocol] can access from Mac/Win but not from Linux

[Duke]

Hi folks,

Here at our institution, we have a windows server that has a share, and 
I am able to access this share both from Mac and Windows:

Mac: cifs://host.domain.com/share_directory
Win: \\host.domain.com\share_directory

but somehow I cannot (or more precisely, dont know how to) access it 
from my linux box. For example, on an Ubuntu box, from Places -> Connect 
to Server... -> Connect to Server box, I chose Service type: Custom 
Location, then cifs://host.domain.com/share_directory, then I got error:

Cannot Connect to Server. You must enter a name for the server.

If I chose Service type: Windows share, Server: host.domain.com and then 
Share: share_directory, and then my username, hit Connect, then I was 
repeadly asked for password, even I knew that I typed my password 
correctly.

Anybody knows what I was doing wrong?

Thank you so much,

D.