[CentOS] NFS /home freezes.

My old nfs server was an old dual Xeon machine running debian. 
Everything worked fine. Then I switched over to a new Penguin Computer 
Altus 2600 (if Im not mistaken) with two Dual-Core AMD Opteron(tm) 
Processor 2210 and 4GB of ram. CentOS4.4 is running on it.

Now here is the thing, this nfs server is exporting "/home" and all 
workstations mount the /home dir via fstab. Ever since I switched to 
this new server running CentOS4.4 everyone on the network gets 5-20 
second freezes sporadically trough the day. In other words if I am 
browsing the net using Firefox, because all the user's options and cache 
are stored on ~/.firefox, it freezes for the 5 to 20 seconds at a time.

After running some test, this happens when big chunks of file are being 
copied via nfs to the server. So as an example if user1 has a 700Mb iso 
image in /tmp and he decides to copy this to his home dir (for whatever 
reasons, this is not important), every user in the network will 
experience 5 to 20 seconds freezes while the file is being copied. Now 
if the same file is being scp-ed to the same user's home dir on the 
server, the freezes do not happen.

Now I have tried many different nfs server options and other nfs client 
options. I also set up a test nfs server with centos4 and 5 where I am 
the only user, and while copying big chunks of date, nfs freezes (hangs) 
too.

Here is my /etc/exports:
/home *domain.com(rw,root_squash,sync,no_subtree_check,no_wdelay)

Here is how client workstations mount the export in the fstab
fshome:/home   /home/   nfs     rsize=8192,wsize=8192,intr 0 0

Am I mis-configuring the nfs server of clients? Is there anything I am 
not doing right?
If anybody has any suggestions, I would appreciate it very much.

Thanks,
Jean Figarella.