When RadGridView is in virtual mode, a StackOverflowException occurs if sorting or filtering is performed.
The issue is duplicated with feedback item FIX. RadGridView - invalid processing of CellValueNeeded event when sorting/filtering is applied in virtual mode. You can track its progress, subscribe for status changes and add your vote/comment to it on the following link: http://feedback.telerik.com/Project/154/Feedback/Details/112031-fix-radgridview-invalid-processing-of-cellvalueneeded-event-when-sorting-filte