IIS W3C Extended Log File Format subclassing...

I am trying to subclass the above file format so that I can add custom code
to filter out certain HTTP requests. My code works on my workstation XP SP2,
however, when I move it to a 2003 server, it hangs on the call to
IntializeLog. Below is my code:
HRESULT CEclaimIISLog::InitializeLog(/*IN*/ LPCSTR SiteName, /*IN*/ LPCSTR
MetabasePath, /*IN*/ PCHAR pvIMDCOM)
{
HRESULT phrtResult = S_OK;

if ( milpIISLog == NULL )
{
CoCreateInstance( CLSID_EXTLOG, NULL, CLSCTX_INPROC_SERVER,
IID_ILogPlugin, (LPVOID*)&milpIISLog );
if ( milpIISLog != NULL )
milpIISLog->AddRef();
}
if ( milpIISLog != NULL )
phrtResult = milpIISLog->InitializeLog( SiteName, MetabasePath, pvIMDCOM );

return phrtResult;
}

The end result is to not change the format of the log file but just to
exclude certains requests. If this is not the correct approach can someone
recommend another?

Thanks in advance.
--
Robert