In recent versions of ZWS, additional CGI security is present to prevent accidental running of CGIs as privileged users or groups.
By default, ZWS won't allow CGIs to run with a GID or a UID between 0 and 100.
However, this can be tuned in ZWS' global.cfg by inserting the below entry
tuning!modules!cgi!minuid value
tuning!modules!cgi!mingid value
This and other tunables are documented here:
http://support.zeus.com/zws/faqs/2005/09/22/what_are_all_the_different_configuration