To reproduce:
- Create a new project and add a blank user control to it.
- Add RadLayoutControl to the user control.
- Add another control to the layout control.

Workaround 
Use a form instead of user control. Then add the controls from the form at runtime. 

To reproduce:
- Add RadPageView with four pages to a form.
- In the firs page add RadLayoutControl with some items in it.
- Select the second page and try to add controls to it.

Workaround: 
- Place the layout control in a separte user control and then add it to the main form.