I experienced that problem on my last computer system. Ever since I switched to my new computer I have not had that problem.
I would try uninstalling eveything including the log files. Then re-install .net framework. I think Konstantine made a post on which file to download for windows 7. Then reinstall the game.
I'm running the same OS Windows 7 64 bit Professional. So I really don't know what fixed it for me other than putting a fresh install of the same windows OS on a new computer.
My guess is that my .net framework install was bad or the wrong version and when I reinstalled my OS on my new system I got the correct version this time.