Since the Q12015 update, if you add a RadCalendar to a project, and try to use the No XAML binaries with the VisualStudio2013 or Office2013 themes, the designer will crash.
Sample project attached.
Available in LIB version 2015.1.0413, it will be also available in the 2015 Q2.
Thanks for your feedback. We managed to reproduce the issue and it will be fixed in one of the upcoming internal builds.
I apologize for any inconvenience caused.