When the Web server attempts to load an ISAPI application, all dependent modules need to be available on the PATH. Because the Web server runs as a service, the PATH must be defined at the system level in the environment settings.
If a dependent module is not found and you are running Personal Web Server, the web browser shows an HTTP 500 Internal Server Error when trying to execute the ISAPI application.
A module commonly not found is the COBOL runtime module, cblrtsm.dll as this exists in your \NetExpress\base\bin folder. ISAPI applications generated by the Internet Application Wizard use the the preferred debug option of statically linking cblrtsm.dll. To ensure that this module is found, you should modify your link settings to use the dynamic binding mechanism.
However, if ISAPI caching has been disabled and you are using the dynamic binding mechanism, the ISAPI application may fail to terminate correctly. In this case, your web browser displays HTTP server errors when you try to run the ISAPI application for the second time. To correct this, try modifying the link settings to link with the static multithreaded COBOL runtime module instead.