I have found a solution that has worked for me, I hope others can make use of it.
I have Linux Mint 13 (Mayo) on my laptop (based on Ubuntu 12.04 which is the LTS version.)
Follow the instructions for Client Authentcation:Ubuntu which can be found within the SME Server Documentation.
When editing /etc/samba/smb.conf the following changes are now required:
Comment out:
idmap uid = 5000-20000
idmap gid = 5000-20000
They are no longer required.
Add the following:
idmap config * : backend = tdb
idmap config * : range = 10001-20000
idmap config DOMAIN : backend = rid
idmap config DOMAIN : range = 10000-20000
idmap config DOMAIN : base_rid = 0
I found it in the Ubuntu forum - see link below
http://ubuntuforums.org/showthread.php?t=2060625&highlight=authenticationI did not find the line
idmap backend = ridDOMAN=10000-20000
if you do then I assume it is not required and can be commented out as well.
I also found that the following line is no longer required so I commented it out.
password server = <ip of sme server>