Thanks for writing and for choosing RadControls for Windows Phone.
From the stack trace it is clear that this issue happens in our list box control. However, it will be difficult for us to determine the reason for the exception without reproducing it on our side. We have never received reports for similar problems in DataBoundListBox and therefore it will be great if you manage to gather some more information about the scenario in which the exception occurs and share it with us.
Let us know if we can further assist you or in case you have any questions.
Thanks for your time.
All the best,
the Telerik team