You say you are trying to install via an nfs mount. Your reported error indicates that the nfs mount is failing on the client. You need to verify that you have properly setup nfs on the machine that you are trying to install from.
To verify that the nfs server service is running on the system you are trying to install from, run "service nfs status". If this indicates an error, you do not have your nfs server properly set up to share your installation files.
If the nfs service is running properly, to verify that the installation files are properly shared, on the nfs server run the command "showmount -e localhost". This will display all of the directories that you have configured to nfs share from this server, and the clients that you have authorized to share them to.