What's with CreateProcess and managed exes?

I have some code that launches another process in a suspended state, does some stuff (tm) and then resumes the process. This uses CreateProcess() and works fine on unmanaged exes. When I try and launch a manged exe with the same code the process starts up in a running state rather than in a suspended state. The docs for CreateProcess() don’t mention any strangeness. Does anyone know of any docs that explain what’s going on?