I have VS2010 and VS2012 installed on my computer and had the .NET Framework 4.0 which I then upgraded to .NET Framework 4.5. However, I am still developing apps that need to w
Time to punt this question. I'm no expert on WPF, don't like it much for exactly these kind of problems, debugging dependency property problems is a nightmare. But I'm pretty convinced you are chasing a ghost. WindowState has been a dependency property all the way back to 3.0, nothing special happened to it in 4.5 that I can see or ever heard of.
You got some kind of error message that nobody can see that convinced you that it had something to do with the binding. I'm from Missouri, the Show Me State. Well, close enough to Wisconsin.
Spend more time working on code that gives you a reliable exception message and stack trace that helps you diagnose errors on the machine you deploy to, the one without a debugger to help you figure out what's going wrong. You do so by writing an event handler for the AppDomain.CurrentDomain.UnhandledException event. Log or display the e.ExceptionObject.ToString() return value. It gives you the exception message and the Holy Stack Trace. If that doesn't help then update your question with what you saw.