Problem with mounting NFS on Mac OS X

Recently, I got a problem mounting my NFS shares. A shortcut to the /Volumes/Public placed on the desktop would mount the volume in read-only mode. A go to /Volumes and selecting the Public link would mount it in read-write.

Things I tried first:
-chgrp to guest, admin, 20 (group where my user is)
-chown to guest, myself, admin
-chmod to 777

Once a volume was mounted in read-only mode, it would only come back on read-write mode after a reboot of the NFS client and following the manual process. It must have been a while like this but it went unnoticed as when mounting from an application (not Finder), it would mount correctly.

I tried rebooting the QNAP (shame on me) but it would not change the mounts without rebooting the client.

So what did I learn so far. All NFS mounts are cached on the client. If you know how to clear the cache without rebooting, it would help me.

I also run nfsstat to find a lot of problems. Compared to some production systems, the number of nfs problems is abnormally high. (I will include some statistics to prove my point.)