IIS Acees detailed logs??

Hello!
I developped an ISAPI application (based on POST Multiform-data request). We succeed in calling this application from IE, or from a Windows-based C++ client. The problem is the following one: we would like to access this ISAPI application from a Linux-based Java client. We succeed in calling it from a Linux web explorer. But, when trying to access it programmatically, a GET request works, but not a POST request.
And, on the IIS server logs, we do not see any log of the POST request.

Does anybody have an idea of the problem?
Does anybody know how to know why the POST request has been denied by my server?

Thanks for your replies....

Julien.