Hi Francis
I have the exact same problem ....
It's no so much a Netbackup issue, more like Solaris.
Netbackup is trying to export your ZFS SRT to the Solaris 9 client. It should fail, since Solaris9 boxes won't be able to handle ZFS.
The first error output you have is from Solaris share command that need to be applied to UFS file system. Not ZFS.
What you would like from Sun is a little more specific error output like
"Can't share ZFS file system"
Only solution to the problem is to create any pre Solaris 10 SRT in UFS , not in ZFS.
The only thing you could expect to get from Netbackup is a better problem detection like
"Can't create Solaris9 SRT in ZFS , please use UFS"
or something simular.