Freenas + NFS + SBS 2011 = impossible

[keebs]

I need to access an NFS share on FreeNAS from my SBS 2011 OS.

- I've installed the Services for NFS and Identity Services for Unix.
- I can also mount the share to a drive letter without issue.
- I can view existing directory and file listings, create & delete directories & files, but I cannot read file contents or copy file contents to the NAS - the files are all 0 bytes.

I believe the problem has to do with the user UID and GID in AD.

Can anyone help?

TY