Samba client problem with concurrently open files

[digital man]

I'm having a problem with the Samba client for Linux (Red Hat 6.2):

I mount a Windows share on my Linux box and run my portable application that
opens files (and leaves them open) and uses record locking to prevent data
corruption. The problem is that writes from the Windows machines to a file
that is currently open on the Linux machine do not show up in the Linux
application until it (the Linux app) closes and re-opens the file. Writes
FROM the Linux app show up on the Windows machines immediately (no
close/re-open necessary) and writes from the Windows apps show up on the
other Windows machines just fine, so it doesn't appear to be a problem with
the configuration of the server (WinME).

I've tried the following smb.conf settings which have failed to solved this
problem:

oplocks = false
strict sync = true
sync always = true

It sounds like a file caching problem, but the solutions shown on the Samba
FAQ seem to be related to Samba Server (not client).

Any help would be much appreciated,

Rob