I'm running smbclient on Ubuntu, trying to connect to a Windows box, and I'm getting "session setup failed: NT_STATUS_LOGON_FAILURE".
I've verifed that I can ping the box and telnet to ports 139/445, so I'm pretty sure that it's not a firewall issue. And my client says that they can connect to this Windows box from another Windows box with the userid/password combination without issue. Also, this box can connect via smbclient to other Windows boxes that this client has.
Any other ideas for why this isn't working?