Our clients are getting this error in the dropdown. Please help us figure out this issue.

System.Threading.Thread
System.Exception: Internal error: can't convert to DestinationValue.
   at Infragistics.Win.EmbeddableEditorBase.GetDataFilteredDestinationValue(Object sourceVal, ConversionDirection direction, EmbeddableEditorOwnerBase owner, Object ownerContext)
   at Infragistics.Win.UltraWinGrid.UltraCombo.get_Value()
   at Infragistics.Win.UltraWinGrid.UltraGridComboEditorOwner.GetValue(Object ownerContext)
   at Infragistics.Win.EmbeddableEditorBase.GetDataFilterSourceValue(ConversionDirection direction, EmbeddableEditorOwnerBase owner, Object ownerContext)
   at Infragistics.Win.EmbeddableEditorBase.GetDataFilteredDestinationValue(ConversionDirection direction, EmbeddableEditorOwnerBase owner, Object ownerContext)
   at Infragistics.Win.EditorWithCombo.GetElementValue(EmbeddableUIElementBase element)
   at Infragistics.Win.EditorWithCombo.GetElementText(EmbeddableUIElementBase element, Boolean ignorePasswordChar)
   at Infragistics.Win.EditorWithTextUIElement.PositionChildElements()
   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)
   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)
   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)
   at Infragistics.Win.UIElement.VerifyChildElements(Boolean recursive)
   at Infragistics.Win.ControlUIElementBase.VerifyIfElementsChanged(Boolean verify, Boolean syncMouseEntered)
   at Infragistics.Win.ControlUIElementBase.get_CurrentCursor()
   at Infragistics.Win.UltraControlBase.get_Cursor()
   at System.Windows.Forms.Control.WmSetCursor(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)