Multiple Scenemanagers not working

Using MOGRE, when I try to switch SceneManagers using this code:
RenderWindow.RemoveAllViewports();
RenderWindow.AddViewport(Camera)
some of the time it will quit, saying, "AccessViolationException..." on my root.RenderOneFrame line, or it will say something about a debug assertion

I got some AccessViolationExceptions also when RenderOneFrame is called, but I fixed it, I had some error with compositors.

Well I don´t know why you get that error, but you can try to use the debug dlls of mogre and enabled the native debugger in the project settings of visual studio. this maybe can give you some information if you look at the stack.

OK, I fixed the AccessViolationException, now its just that I get a debug assertion error about 1 out of 4 switches