Manually adding schema extensions (NDS 8.85c)

Trying to install NFS 3.0 on Netware 5.1 SP7 with NDS 8.85c, 'SCHINST.NLM'
fails:

Error: "Failed to add schema attribute UNIX:UID. An error occurred
modifying the NDS schema for file sys:system\schema\nds4s.sch.
Error Description unknown error -708 (fffffd3c hex). (DSI-5.00-185)."

All documented workarounds tried with no success.

Can I somehow use a tool like NDS Schema Manager to manually add the
extensions using the data in sys:\system\schema\nds4s.sch? If so
is there a paper somewhere that describes the procedures and
cautions to follow?

Thanks,

Michael Grigoni
Cybertheque Museum