thanks for the replies, but now I'm confused about how to proceed. Should I submit a support ticket or apply the update? If the latter, how do I apply the update, exactly, and is there any danger of data loss? Sorry to admit that I have very limited experience with these systems.
you may upload the update in the webGUI at MAINTENANCE-->Software updates. Reboot for it to be applied.
After reboot the system will mount with inode64. You will also need to go to each share and set the FSID for NFS. This is a number, and unique to each share.
If this solves your problem, great. If not, you may open a support ticket.
Also be aware that changing to inode64 it is recommended to stay with it. If in the future if you remove the small update some data may become inaccessible.
after successfully applying the update and setting FSIDs for the two shares on the system (FSID 1 and FSID 2, respectively), I remounted the share in question and found that I still get the "No space left on device" error. Did I miss something? Should I try updating the the latest version of DSS 6 followed by a filesystem repair as suggested by Todd? Or ... ?