nfs: server not responding still trying - Linux stops

There was a similar message before in this group but there was no
satisfying answer or it is unreachable.

I have received a RedHat Linux box from Dell and it shows these
annoying symptoms of ultrahard nfs mounting over the network. Whenever
one of the other workstations is down the Red Hat Linux box stops
working. The only way to continue is plugging off the computer.
I have a Suse Linux box in the same network which doesn't show any of
these problems.

How do I have to change the configuration? What do you recommend?

Thanks
Carsten