Personally, I'm a c++ and python guy, and I would probably go with c++, because this sounds like a relatively intensive project, and I do most of my best high level design in C++ (great for building fast, flexible code base), while I tend to use python for things like django, where there is less application logic, but being able to tune the function, look and feel quickly is very important. However, my choice doesn't mean it should be your choice. Here's a few things to consider:
Foremost 1) Familiarity. If you are coding production code, you want to go with something you know, and works well for you, or you'll be struggling with the language and be missing deadlines. And even when you complete the project, you are bound to have a lot of messy code for things you were learning. I'm all for learning new languages, but make it on something you can afford to screw up on.
2) Third party libraries; which ones do you want besides the one you mentioned? If they don't have wrappers, you'll be rolling your own. What you want to write your GUI in would be an example.
3) Deployment: I assume this will be an assumed windows executable. C# and C++ both do this easily, but you'll have to be familiar with py2exe if you are planning on deploying a python program without a python interpreter
