samba - Nov 2008 - "users" or "valid users" in share declaration.

Hi List,

Here is a small snip from my config:

[homes]
  comment = Home directories
  browseable = no
  read only = no
  create mask = 0700
  directory mask = 0700
  valid users = %S
  hide dot files = yes


[shared]
  comment = Shared by all SREC Engineering employees
  path = /data/shares/shared
  create mask = 0770
  directory mask = 0770
  users = %S
  force group = users

Note the valid users = %S in the [homes] section and users = %S in the 
[shared] section

First I had valid users = %S in the [shared] section and windows was 
giving me an error saying that there was more than connection with the 
server etc. etc.
Almost by accident I changed it from valid users to users after which 
things started working perfectly.
With the valid users directive in [shared] I had an H: drive but could 
not map anything else...

So my question is what is the difference between users and valid users?
And do I 'change' it in the [homes] section too ?

Thanks

Peter