NFS Version 4 lock interfaces

Hello,

          Been testing some NFS Version 4 exports from my RHEL 4 server

mounted by  various FC13 & Scientific Linux clients.

  Have found that applications such as Firefox reported they couldn't obtain

locks...

  Closer investigation has shown  that the fcntl(2) system call is failing  with error no. ENOLOCK. By contrast the flock(2)  lock interface is working. 

 I found a bug report relating to RHEL5 that indicated this might be a kernel issue.

Has anynone been able to get this working under RHEL4?

 The kernel I am currently running is 2.6.18-164

Thanks in advance for any experiences related,

                                                                        David.