This is one funny thing I found while fiddling around with WPF, Cider and the other parts from the newest CTP release: every now and then it’s required to rebuild the complete solution. I suppose it’s not meant to be that way, but I’ve had all kinds of interesting effects. One time there was a weird exception coming up at runtime, telling me that a Button can’t be cast to a ListBox. The other time it was just some initialization code for a control that was apparently being executed, but didn’t have any effect. Rebuilding the complete solution helped in both cases and my guess is that the problem came up when I made some changes to the XAML code of a window.
So if your WPF app seems to behave oddly, always remember rebuilding the solution – it might help.