using NFS with Mac OS X

I have a small home network consisting of just two machines.

One machine is an Intel system running RedHat Linux 9. The other is a
Macintosh G4 running Mac OS X 10.2.6.

Fundamentally, the network seems to be work as the two computer can
ping each other. I would like to two machines to be able to
communicate with each other using NFS.

For the Macintosh I downloaded a shareware application named NFS
Manager and used that to configure NFS on that computer.

For the Linux system I use the how to tutorial found at
http://nfs.sourceforge.net/nfs-howto/ to it up as an NFS server.

I seem to have NFS working correctly because I can mount the NFS share
points locally. That is that I can mount the Macintosh NFS share on
the Macintosh, and I can mount the Linux share point on the Linux box.

What I haven't been able to do, is get the share points to mount
across the network onto the other corresponding computer.

When I try to mount the Macintosh share point on Linux, the computer
will wait for several minutes and then respond with:

mount: RPC: Remote system error - Connection timed out

When I try to mount the Linux share on the Macintosh it seems content
to display the "Connecting To Server" dialog forever, until I click
the Cancel button.

What do I need to do to get NFS working correctly?