Paul Harter wrote:

To use python.net with it is fine as long as the initial import of clr takes place early on in the main thread. Otherwise it doesn't work on multi-processor machines. I don't know why.

import clr should always be the first thing you do in an app. "import clr" loads and initializes the Python.Runtime assembly. During the initialization Python's __import__ hook is replaced with a custom hook for the CLR import magic. You can get in all kinds of trouble if you replace __import__ in a thread while another threads tries to import an assembly. Our you can suffer from an import dead lock. It's a race condition. In an embedded .NET or C/C++ app you shouldn't use clr. It's better to import the Python.Runtime assembly and call its PythonEngine::InitExt() static method. The sample implementation in https://pythonnet.svn.sourceforge.net/svnroot/pythonnet/trunk/pythonnet/src/... contains a working example and some helpful notes from me. I run into a problem with threads, too. Christian