Hi drumoyne - it seems to me that mitsubishi 3D ready TV's are simply not compatible with TriDef no matter what your PC system. Mitsubushi recommend nVidia Geforce 3D vision (in fact they were both developed to be compatible with one another) where as TriDef paired up with Samsung and therefore those systems are compatible.
Trying to make TriDef work with your Mitsubishi is a case of putting a square peg in a round hole - it's not going to happen.
Can you get a refund on the TriDef software and go for the nVidia system instead? That would make more sense to me. As long as your PC meets nVidia's system requirements it will work perfectly on your Mitsubishi.
Hope this helps :)
P.S. It's better if you ask me questions in the comment section on the article http://hubpages.com/hub/3d-ready-tv, since I can only reply once to a question. Your questions and my answers will also help other people who aren't sure what to do.