I've been trying to get Samba (cifs) to mount our Windows 2003 Active Directory file server for about a year. I've never had any luck until a coworker found that it required NTLMV2.
mount.cifs //10.1.0.5/HomeFolders/baker_s /mnt/network_drive -o credentials=/etc/credentials,sec=ntlmv2 -v
Put very simple credentials in /etc/credentials and then chmod 600 the file.
#/etc/credentials domain=mydomain username=baker_s password=sekrit_password
Or the coresponding fstab entry:
//10.1.0.5/HomeFolders/baker_s /mnt/network_drive cifs credentials=/etc/credentials,sec=ntlmv2 0 0