Connection through system proxy (unity 4.0 problem)

Hi Guys, today we faced a new bug after compiling our in3dconfigurator platform with Unity 4.0 (mac standalone build).

We are facing problem reaching the internet through a system proxy. The same application compiled with Unity 3.5.6 doesn't' give any problem.

With the new build (in unity 4) I receive the following answer from the connection to the server:

Connection Error 407 proxy authentication required ( forefront TMG requires authorisation to fulfill the request, Access to the web proxy filter is denied )

With the build made with 3.5.6 I reach the update server without any problem.

Could you please give me an advice? there is a way to force the usage of system proxy? or there is a way to input a proxy address inside the application itself?

Thanks