It is a worth a try to uninstall and reinstall the .NET Framework. The Modeler works with Microsoft .NET Framework 3.5 Service Pack 1.
I've got the same problem. The modeler crashes when I enter the app store. Working on .NET framework 4. Would that be a problem?
From comments: Did the 'downgrade' but was not helpfull. After a lot of searching saw a message in Windows 7 System Event manager stating that nvidia driver was causing the problem... Driver update works... Thnx!
Have you tried to run it with administrator rights?
I have and it still gives me the same error. Earlier on I ran a system restore to a point before installing the Mendix application. I then installed it again and the result are still the same (It bombs out)