Yeah, I was barking up the wrong tree...It's because a telnet session I was running was "too fast" to delete a file before sending the next command (earlier in the script). I used a timeout attribute. This explains the *intermittent nature* of the problem.
When it couldn't download the file, that it needed to my "custom ant script" didn't have the input that it needed and thus I got some obscure error message that had nothing to do with the problem.