check if nfs is running on the machine from where to mount nfs-share:
ps aux | grep rpc -> rpc..mountd etc. should show
ps aux | grep nfs -> nfsd should show
use the command
<control-panel &>
to automagically have portmap and nfs started.
you can fall back to manually do /etc/rc.d/init..d/portmap start
or
/etc/rc.d/init..d/nfs start
A perhaps interesting and also security-concerned related article is
here
CC.