Users can only read but not edit new files - 4.2.19 nogroup

ewok: when user Len creates a new file in the share, using Windows7 (or XP)

With the Share Folder Owner set to "users" in advanced Options file permissions in Windows look like this:
Group or user names:
Everyone
users (Unix Group\users)
Len (RNAS1\Len)

With the Share Folder Owner set to "nogroup" in advanced Options file permissions in Windows it used to look like:
Group or user names:
Everyone
nogroup (Unix Group\nogroup)
Len (RNAS1\Len)

I then changed the Advanced options from nogroup to users, and back again, but no matter what this is set to I now get the following:

Group or user names:
Everyone
users (Unix Group\users)
Len (RNAS1\Len)

Also, access to shares seems to be ignoring the settings for users and groups, using a couple of test shares. Perhaps I need to reboot the readyNAS and have another go. It would help to know for sure how it needs to be set.