I was having trouble getting my Lion machine to connect to my fileserver via NFS. It turns out the fix is really easy, once you find the random forum discussion that mentions what config you need to change.
In your /etc/exports file on the server, add “insecure” to the options, which just means that requests are allowed to come from ports >1024, which apparently the NFS client on mac does. It’s not actually insecure.
My exports file now looks like this: