[CentOS] NFS Mount - RH7.3 Server - CentOS 4.1 Client

Hi

Just upgrading one of my dev servers - I'm replacing a current box that 
runs 7.3 to one that runs CentOS 4.1

Currently the 7.3 dev box talks to a fileserver also running 7.3 over 
NFS and that works fine. I'm now trying to get the CentOS 4.1 box to 
talk NFS to the 7.3 server.

When i try and mount the NFS share on the CentOS box i get the following 
error

# mount /mnt/cvs
mount to NFS server 'Server Name' failed: server is down.

Now i know the server is not down as the 7.3 client is connected fine. 
Anyone seen this before or know a work around? Nothing in any logs from 
client or server to give me any hints?

thanks