mount: blue server not responding: RPC_PROG_NOT_REGISTERED

It means that mount got through to the portmapper, but the NFS mount daemon mountd was not registered. Check the server to ensure the /etc/mountd exists and is running. On linux systems, NFS isn't always turned on after an upgrade. To turn it on run, /etc/rc.d/init.d/nfs start. To make sure it is always running, run chkconfig --level 2345 nfs on.

Another error might be RPC_PMAP_FAILURE - RPC_TIMED_OUT. This means that either the server to which the mount is being attempted is down or its portmapper is dead or hung. Attempt to log in to that machine; if you succeed, then the problem may be in the portmapper. Run the following command from your system as root to test the portmapper on the server system.

rpcinfo -p hostname

If the resulting display does not show portmapper, stop and restart NFS on the server. /etc/rc.d/init.d/nfs stop/start.