Access denied on some files on Win2008R2 DC share

Solution 1:

If you run AccessEnum against that user's shared folder, does it show any changes to permissions deeper in the hierarchy? By default this tool shows only files which have more lax permissions than the parent, so try going to Options → "File display options" and choosing "Display files with permissions that differ from parent".

At worst this will rule out any problems with ACLs on the file system; at best, it might uncover a file permissions problem that went unnoticed.

Solution 2:

Although the user is not part of the domain, it does not preclude them for connecting to domain resources as "domain"\"account" (e.g. domain-name\user-account) - is that occurring?