>Symptom: mount succeeds, but file operations (e.g. mkdir) fail.

I don't have any problem with my machines:

SunOS fluorine 5.7 Generic_106541-02 sun4m sparc SUNW,SPARCstation-10
# share -F nfs -o rw=lithium -d "fluorine root" /

NetBSD lithium.local.domain 1.4.1 NetBSD 1.4.1 (3MIN) #0: Sat Oct  9 21:20:08
EDT 1999 kevin@lithium.local.domain:/usr/src/sys/arch/pmax/compile/3MIN
pmax
(with 1.4 userland)
# mount fluorine:/ /mnt

Everything I've ever done (mkdir, read, write,...) has worked. nfsstat
confirms it's using version 3. If you supply your share and mount
options, I'll try the same.

-- 
Kevin Schoedel
schoedel@kw.igs.net