I've got two machines running 2.4.17, this has been a problem all through
2.4.x.  I have one machine, workstation, setup to mount directories off of
another machine, disk.  I can mount them just fine directly and with autofs.
However over time I get stale NFS filehandles for no apparent reason.  Neither
machine was rebooted or lost a network connection.  Most recently I reproduced
this behavior by mounting one directory, leaving it for a long time without
much activity, then checking it; everything was ok, so I mounted another
directory and suddenly any files open on the first mount came up with stale
NFS filehandles.  So I kill off what has the open filehandles and umount the
directory to clear the stale NFS filehandles.  Then I try to mount the
directory again and disk shows the following in the message log until I run
exportfs -ra:
Dec 29 22:49:32 disk rpc.mountd: getfh failed: Operation not permitted 

I've tried NFSv3 on and off and neither seems to help.  I'm at wits end here.
Anyone else have ideas?

-- 
Jon Schewe | http://mtu.net/~jpschewe | jpschewe at mtu.net
For I am convinced that neither death nor life, neither angels 
nor demons, neither the present nor the future, nor any 
powers, neither height nor depth, nor anything else in all 
creation, will be able to separate us from the love of God that 
is in Christ Jesus our Lord. - Romans 8:38-39