You're probably running a Webinator built for SCO version 5.00 on a machine which is running a different SCO version. SCO is particularly incompatible from version to version, even minor revisions (eg. 5.00 to 5.02) and often executables built for one version won't run on another due to errors like this. You can find your OS version by running uname -a.
You'll need to move to a SCO 5.00 machine, or another operating system supported by Webinator.