Backward Compatibility
Telerik RadMaskedInput suite of controls - Q3 2011
The value of the KeyboardNavigation.TabNavigation property isn't used in the RadMaskedInput controls tab navigation implementation. From now on you need to set the SectionsNavigationMode property in order to configure the tab navigation in the RadMaskedInput controls. You can find more information about the SectionsNavigationMode property in the Keyboard and Mouse Support article.