I did not find this in archives, so a quick report. My apologies if I missed it.
NFS server SL5.9 with kernel 2.6.18-348.1.1.el5

Problem: NFS client (SL6.1) would see multiple cookies for some files and directories. dmesg reported one directory in particular and a few files. All files in that directory repeated 3 times. 2 of 3 directories repeated 3 times. One directory missing on the NFS client side.

Original file system fine. Directory listing correct. Older SL4.9 NFS client fine.

Google search yielded:
https://bugzilla.redhat.com/show_bug.cgi?id=739222
which indicated a problem with this specific kernel (2.6.18-348.1) and that reverting to 2.6.18-308.24.1.el5 solved it.

The reported problem was different than mine, it seemed to be specific to directories with a large number of files (160K), whereas, my directory had 167.

Anyway, my NFS client problem solved by reverting to the next oldest kernel (2.6.18-308.24.1). 

What is the easiest way to track if updated kernels "fix" this issue other than trying them out.

Bill Lutter