I've occasionally had to get drivers from very large cab files, usually DELL ones. This takes so long in Windows, so I do it in Linux once using cabextract and then I can share it using the samba server, rather than extracting on every Windows machine. This is a great piece of software, very useful. It's really simple to use.
Despite the UID permissions working correctly, and all the UID/GIDs matching up perfectly, a Ubuntu file store I was exporting via NFS would not work with the existing group permissions of the client. To solve this, on the NFS file store, comment out;
--manage-gid option from /etc/default/nfs-kernel-server. Restart nfs-kernel-server and it all should work fine.