Problem to auto mount on NFS server

I am new in Ubuntu and i use Ubuntu 7.10, and have problem to mount automatic when i reboot computer,

Here is my /etc/fstab

192.168.0.91:/home/DATA/it /home/USER/usertest/Documents/Z nfs defaults 0 0

I try many option in that line, but the result is same, I cannot automatic mounting the NFS server when i reboot the computer.
I Read ubuntu documentation, seems that i dont miss any steps.

Is there any mistake? because usually I use other distro(redhat, fedora) has no problem with same configuration.

Thank you.

What happens when you type

mount /home/USER/usertest/Documents/Z

I can mount the NFS server, everything fine, i can read and write too.
The problem is when i restart my computer, seems that fstab cannot read my line.

Or, it can read your line, else mount would not work, but the nfs services required may not be ready.

Do you have an initialisation script that runs towards the end of booting up that you could add a "mount -a" or "mountall" or equivalent?

NFS server, is running well. Any system mount to NFS server without problems.

Good idea, I try to add "mount -a" in rc.local, like your suggestion, it's work.
But i think this solution is little bit strange. In other disro, even in BSD everything fine, when I just add line NFS mounting in fstab.
Can you explain to me? why it could happen.

Thank you @porter.

You would need to analyse your system boot up, I suggest start with the system message log.