Setting SelectedIndex property of combobox resulted in "Specified argument was out of range" exception

While working on a SketchFlow prototype, I got this exception
"Specificed argument was out of range"
when attempting to set the value of ComboBox.SelectedIndex in the LayoutRoot_Loaded event handler. It used to occur randomly, so I concluded that this could be the result of some behavior not entirely under my control.
I got rid of this exception by setting the SelectedIndex propertly in the ComboBox_Loaded event handler. Hope this helps someone there with a similar issue. :)