We're experiencing the same problem with the latest controls (Version 2011.2.712.1040).
The RadComboBox's SelectedItem is bound to a property on the ViewModel.
However the property on load is being set to Null by the RadComboBox.
Our RadComboBox sits within a ControlTemplate....
...and the RadComboBox sits within a Grid.
When we replace the RadComboBox with a normal ComboBox control - the problem goes away.
Is there a fix for this - we really would like to keep using the Telerik RadComboBox.
EDIT----Further to this...
If I open my EditAppointmentTemplate every alternate time it works. I do not select another appointment in between this.
Open 1st time - RadComboBox sets the property to nulll.
Open 2nd time
- RadComboBox gets the property correctly - based on RIA value
Open 3rd time -
- RadComboBox sets the property to nulll.
Open 4th time -
- RadComboBox sets the property correctly - base on RIA value