Before I send the developer off to pound on Synopsys about the problem, does Data OnTapp 5.2.1 have a filesize limitation? I seem to remember reading "not since v4.n" (and a given value of `n'), but now I can't find that reference.
The value of "n", in this case, would have to be "1, and then shift left two characters and add 1"; the first release in which files >4GB are supported is 5.1.