wfp inside Windows service

Question

I am calling a VC++ DLL from a windows service that was written in C#. The DLL handles all interaction with the WFP. When compiled as a console app, everything works fine (as long as I run as administrator). When compiled and ran as a service, the DLL fails on FwpmEngineOpen0(). This is the same symptom that I received when I didn't run the console app as admin. Are there permissions that I need to assign a service to run as admin? This is being built under Win 7 with VS2008.

This is what I am using: return = ::FwpmEngineOpen0( NULL, RPC_C_AUTHN_WINNT, NULL, NULL, &engineHandle );

Thanks in advance!