For me, I updated to client 4.9x and the problem went away.... This was a year or so ago...
>You might also want to see how deep the files are in the directory hierarchy -- i.e. what's the length of the full path. If the full path is too long you could get this sort of problem in some software (IIRC, the DOS limit was around 64 characters). And yep, I've seen this problem on our configuration here (we've got a Novell server) -- the strangest problems occurring back before I applied the long filename patch (to make it use Win9x style short filename rather than simply truncating the filename).
State of Florida, DCF