I had a weird problem with my computer and .NET Windows forms applications. Every time that I would select another window and then reselect the .NET application, the app would cause a NullReferenceException.
This occurred even with the simplest application (i.e. the one created from the Visual Studio wizard). I had thought something had corrupted my .NET or Visual Studio installation.
I was looking at uninstalling and reinstalling everything, but I decided to do some googling. I finally came across a reference in the newsgroups that mentioned the Kensington mouse driver and I thought “Hey, I have that mouse”. Sure enough, uninstalling the Kensington driver fixed the problem. I am glad that I went googling for a solution as I would never have guessed that the mouse driver could be responsible for that kind of problem.
I was so thankful, I made sure to send an email to the person who posted the solution to thank him. Now I am posting the problem and solution to make it easier for the next person to find the solution.