Protected Share not accessible - Windows Explorer

@nbsimmo:

Your settings seem right, at least per an old Netgear KB article. Your settings are the same as "Setup B", correct?

Setup A: Specific users have read/write access; guest users have read-only access. From the Default access drop-down, select Read-only. This will prevent other users or anonymous users from editing or deleting items on the share. Enable the "Write-enabled users" checkbox and enter a user or group name in the associated textbox. Enable the "Allow guest access" checkbox to allow anonymous users to login to the share. Setup B: Specific users have read/write access; no guest users allowed to access share. From the Default access drop-down, select Read-only. This will prevent other users or anonymous users from editing or deleting items on the share. Enable the "Write-enabled users" checkbox and enter a user or group name in the associated textbox. Disable the "Allow guest access" checkbox to prevent anonymous users from logging into the share. Setup C: Specific computers have read/write access, regardless of user. From the Default access drop-down, select Read/write. This will grant permission to users to edit or delete items on the share. Enable the Hosts allowed access checkbox and type the IP address that is allowed to access the share. This option restricts access to the share to the computer associated with that IP address. Disable the "Allow guest access" checkbox to prevent anonymous users from logging into the share.

Have you tried resetting the underlying file permissions (which are different from the share permissions)? Generally you want to set the file permissions to grant everyone permission, and restrict access using the setups above.

So try going into the "advanced options" tab (far upper right) and set

Share folder owner: nobody
Share folder group: nogroup
Share folder owner rights: read/write
Share folder group rights: read/write
Share folder everyone rights: read/write

Check the two checkboxes directly underneath

Set ownership and permission for existing files and folders in this share...
Grant rename and delete privileges to non-owner of files.

Then click apply (lower right). The checkbox next to "set ownership" will clear, and ownership is reset as a background task. There will be a pop-up when it completes.