smbclient + Win 2003 Server = Problem

[Igor]

When trying to mount a share from the server running Win 2003 Server, the 
following messages appear:

otdel4 at nt2 otdel4]$ smbmount //server5/Lotus /mnt/smb/ -o username=otdel4 
cli_negprot: SMB signing is mandatory and we have disabled it. 
3823: protocol negotiation failed 
SMB connection failed

But mounting shares from the servers running other OSes (NT4.0/2000/9X/Me) 
works as needed. 

Would you help me - what's wrong?

The samba version is 3.0.4, built from the src.rpm (downloaded from the 
samba.org server) on the machine, running Red Hat Linux 9.