Thanks for the feedback. I think the problem is related to propagating changes across threads.
Such problems are very well explained in the following blog post: http://www.beacosta.com/blog/?m=200609
I modified a little the Beatriz Costa's example and just changed the ListBox control with Telerik RadGridView for WPF and all seems to work fine. See attachment for the modified example.
Should you have any additional questions/problems don't hesitate to contact us.
the Telerik team