Tru64 NFS server problems with recent Linux NFS clients

We have an Alphaserver DS25 NFS fileserver running Tru64 UNIX v5.1B
Patch Kit 4 (we will upgrade to PK5 shortly).  In recent months
we've been having some serious NFS problems on many Linux clients,
since we started upgrading them to the latest Linux versions
such as Redhat RHEL 4.0 and Centos 4.1 (all running the Linux
kernel version 2.6):

Too often the NFS client hangs waiting in NFS I/O on the users'
home directory, as soon as the user logs in to the graphical
desktop (GNOME or KDE).  Removing the user's GNOME or KDE
setup and rebooting the NFS client will in many cases solve
the problem, but the apperance of the problem seems to be
erratic and irreproducible.  If the client is turned off
for some minutes the problem sometimes goes away, so there
may be a timeout factor involved.  There is nothing in
the Tru64 server's /var/adm/messages which points to any errors.

Older Linux NFS clients running the Linux kernel 2.4 have
no such problems with this particular server.

We suspect that some new features in the Linux kernel 2.6
and/or GNOME and KDE is triggering a bug in the Tru64 UNIX
NFS server.  We have not heard of similar problems with
Linux NFS servers.

Question:
Has someone else got experience with Tru64 NFS servers and
Linux NFS clients (recent kernel 2.6 versions only) ?
Is there a workaround or patch which solves this NFS problem ?

Thanks a lot,
Ole Holm Nielsen
Department of Physics, Technical University of Denmark