I suspect that you are having trouble with the way Windows handles NTFS permissions when you move files. Permissions on an object (folder or file) are inherited from the parent folder when the file is created. However, when an existing file is moved to a different folder on the same volume, the original permissions are retained. Your files were probably originally created in a folder with more restrictive permissions (perhaps under "My Documents"), then moved to the shared folder. That could result in the problem you describe.
With Simple File Sharing disabled, you can quickly fix it by resetting the permissions. Right click the shared folder, Properties, Security tab, Advanced, tick the box to "Replace permission entries on all child objects..." and Apply. You will be prompted to confirm and permissions on everything in the folder will be reset.
If you wish to change how Windows Explorer handles permissions when moving files, so that you don't keep running into this problem in the future, you can apply the
second registry change described in
this article.
