Can't see, or access, some folders on NAS Device

My problems with sharing and permissions would take pages to explain. 3 machines, Windows 7 Ultimate, Windows 7 Pro and Windows 7 Home Premium, small work network. Also, a DLink-DNS 325 NAS. I am Administrator on all 3 computers with same ID and password on all 3. I am only person who "manages" the NAS. I attempted setting shares/permissions on the NAS shortly after acquisition (via Windows, not the software of the NAS). I set me to have full control over all folders. Other users limited to only some. Seemed OK. I could see, and access, all folders. Other users could not even see those folders to which they did not have permission (which seemed strange that they couldn't even see the folders in WE). After a firmware upgrade to the NAS, now I can't see, nor access, those folders previously not allowed to the other users. I have tried everything, all to no avail. Also, but not as serious, I have odd, and inconsistent, experience with shares/permissions between the 3 computers, as well. Re the NAS, DLink forum, and Technical Support, no help. I hope I am not out of line in saying this on the forum, but what I am really looking for is a fee consultant I could retain who is a legitimate guru in Windows 7 Permissions. It is driving me nuts. As I said, it would take pages & pages to specify the details and I wouldn't expect anyone to have to wade through it for free on a forum. I am located in Los Angeles area. If posting a request for a recommendation is inappropriate in the forum, I apologize and will look elsewhere. If it is not improper, a response indicating one has a recommendation would be appreciated and then I will work it out through a private e-mail.Thanks.

Hi there,

We have a few NAS'es in our network and so far all is well. I have created Users/Passwords with the same LogIn from their Windows and have given them appropriate permission. I'd also look on the hardware part (i.e. NIC, Switches). The NICs are usually set to auto-negotiation, have you tried changing this to 1000Mbps/100Mbps full? I was hoping that you are using using wired connection to access the shared folders.