VS2013 WPF designer not responding after even simple save

Question

In my WPF application, whenever I make some changes to XAML, either XAML for controls or resource, after I click save, it takes long time, I mean the VS freezes for really long time, during which both the VS window and task manager show "Not Responding". "Clean solution" also makes it not responding for long time. It can't be that I am running out of memory since I have 24GB RAM and in the Task Manager it says currently only 35% of the memory is being used.

I suspect it has something to do with initializing the design-time DataContext for my UserControl. Because when I only have non-UI files opened I never have this problem. But the worst thing about this problem is I don't even know where to begin to solve it. Can anybody help me!