Thank you for contacting us.
The Q3 release of RadControls for Windows Phone requires Windows Phone SDK 7.1 (it shows a warning message at the beginning). Could you please check if you have the Windows Phone SDK 7.1 installed? If not, you can download it from here.
If you have the Windows Phone SDK 7.1 installed, you can check for some more details in the output window after building the solution.
Let me know if the problem persist.
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>