To reproduce: After upgrade from Q2 2014 SP1 to Q3 2014 some controls can not be selected design time because exception that RadBindingNavigator can not be cast to RadCommandBar.
We have just issued a new release - Q3 2014 2014.3.1104, which covers this issue and couple more issues important for our customers. For complete list of changes, please refer to our Release Notes (http://www.telerik.com/support/whats-new/winforms/release-history/ui-for-winforms-q3-2014-(version-2014.3.1104)).