The Command of the MenuItem destroys the binding you set to the IsEnabled property and this cannot be changed. What you could do is to use a TwoWay binding instead of OneWay binding - this way it will not be destroyed.
Another option is to not set directly the command to the MenuItem, but to raise it by hand when the MenuItem is clicked. The easiest way to achieve this is to use a DelegateCommand from your ViewModel and to pass the ScheduleView as parameter. This way you will not need to bind the IsEnabled property of the MenuItem, but manipulate it directly through the CanExecute callback of the command.
Hope this helps.
the Telerik team