Probably your smbpasswd on the samba server?
add a user called Mugs with
Add SMB password with
smbpasswd -a Mugs
(type the password or leave blank for none)
then try connect to it with user Mugs.
or you can replace the User Mugs for whatever the username is on the doze box so you dont have to enter the user in the dialog box. The smb password should be the same as the password on the doze machine.