The following situation:
Usually happens when you use your local credentials to login into a remote server, which have a different password for the user.
$ smbclient //server/share
Enter user's password:
session setup failed: NT_STATUS_LOGON_FAILURE
Often that can be fixed by setting a password on the samba server using the command 'smbpasswd'.
Another alternative is to get the connection either using the full domain name of the user:
Or using the guest account:
smbclient //server/share -U WORKGROUP\user
(password should be 'guest' or empty).
smbclient //server/share -U guest
Let us know how it goes.