Problem accessing file server shares from laptop

Good day to everyone,

First of all, please pardon me if i've created this post where it does not belong. I simply couldn't find a more appropriate place.

A client of mine called me and told me about a problem he's been having. i logged in remotley and found the following problem in all 3 Dell Latitude 6330 Windows 7 x64 Professional laptops he has ONLY:

He could not remotley connect to any folder inside a share in his file server on the same LAN. If he maps that share to a drive at his computer (net use v: \\fileserver\sharename /persistent:yes), it works, but when he tries to enter another folder inside (so it comes out as: \\fileserver\share\folder), he gets the message "*FILEPATH* is not accessible. Access Is Denied".

If he tries to get to the same path using UNC path from the "Run" menu, he will get the error: "You do not have permission to access \\fileserver\share\folder".

Now, that's what i know:

1) No firewalls. AT ALL. Turned off and the service is disabled.

2) No anti-virus affects the sharing\laptops.

3) file, printer and public folder sharing are enabled. For Domain, Home\Work and Public.

4) IPV6 is cancelled.

5) tried Net Config server /autodisconnect:-1.

6) same users can access the share from terminal servers so it's not a permission issue.

7) Ports are open.

8) tried the following smb commands on the laptops:

Set-SmbClientConfiguration -RequireSecuritySignature $true
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" RequireSecureNegotiate -Value 0 -Force

9) Other users, both Domain admin users and non, cant access the shares when they connect through these laptops.

10) tried mapping the netowrk share drives using both gui and cmd, with the "persistent" flag set to "yes".

11) tried to disable the "Miniport" network adapter.

12) Users have local admin permissions on laptops (doesn't seem related to me but thought i should mention it).

13) finally, and a critical piece of information, is that when their System Administrator performs a system restore to a point in time which is very close to when they had only a fresh OS installation, the problem disappears. something happens in between that causes this.

The reason i opened this post here is that i suspect it might have something to do with the laptop's model or any built-in Dell software this model might have.

Any help would be much appreciated.

Goodbye.