TTable causing 'Sharing Violations'

I have a C/S app that uses several dBase 4 files residing on a networked
directory. These files are shared by the instances of this app (using
TTable) I have running on approx. a dozen machines right now.

My problem is that I have started to find 'Sharing Violations' on some of
the more heavily hit files, and I don't know why. Some background that might
be helpful:

    Application was developed in Delphi 4, Service Release 2

    The apps are running on Win NT 4 machines

    I make sure any files that may be written to have to go through a 'lock'
so that only one instance of the app can write to the file at a time
(assuming no bugs exist).

    All of the machines running the app are using the same generic logon

    I do not know what type of architecture the server is running on,
although I believe it is using Microsoft software

I am interested in any theories anyone may have on this problem.

    Jon Gabiou