The problem here, is that you try given access to users that log in in another computers but not in the computer that have the shared folder. This only works with a domain users, and you are working with a local users in each computer. The computer only recognize the users that log in in the computer.
A solution could be sharing the folder across MSN.
You can also make duplicate accounts on the local system doing the sharing with the same name/pass as the other users who need to connect(make then EXACT). Then you can set up the permissions in share and NTFS and be good to go
Do not log into those users on the sharing computer and it will never create local folders for those users(saves space.). you can even hide those users from the welcome screen and user management with a registry trick.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList\ and create a 32-bit dword value the same as the login name of the user to be hidden. Use with care, this user will not even appear on the computer anymore, but will still be usable for shares and ntfs security permissions
Not the nicest solution, but it does the job.
Edit, damn I raised the dead. Just say it in another thread and did not look at the date. my bad