Things like servlets tend to have reduced permissions in ways that can be surprising. For example, you probably can't access a network shared directory. Such might be causing your script to fail. You might want to make sure STDERR of your script gets redirected to an appropriate place that you can check when debugging a failure but that periodically gets cleaned up (and that you are certain can always be written to). Perhaps like:

system("\"$fooDir/bar.bat\" 2>>D:/foo$$.log");
[download]