> He suspects that the back up of some files
>with filenames > 255 characters is causing the problem

Richard - Have that NT guy perform a scan of the file system seeking
          anomalous file names.  Another option would be to perform
a full backup, which will list every name in the file system as the
backup proceeds, and save the log to see where it goes blooey.  That
will at least get him into the problem neighborhood.
    Richard Sims, BU