TypeError: Error #2007: Parameter blendMode must be non-null.
I was working away on an AIR application and all of a sudden I started seeing this error message. It would show up when I had focus on something and clicked a button that removed the component's parent from the stage. As a result of the error, my app would stop working in all kinds of weird ways. For example, TabNavigators stopped working, but List controls worked fine. Some changes to my display list would work ok while others would result in part of the screen going blank.
I will spare the details of how I figured out what the problem was, but the root cause seemed to be that I was compiling my application with the 3.2 Flex SDK but I was compiling one of the Library projects that I was depending on with the 3.3 SDK.
Setting them all to the same version fixed the problem.
I didn't see any other posts through a Google search of that error, so I figured I would post it here.