.NET exception at Bentley.DTM.Element.DTMElementHandlerManager.IsDTMElement(ElemHandle* )

Using Geopak SS4 .878.

I had just created a terrain model. A dynamic cross section model had already been set up. I was clicking through the cross sections fine, but I was tired of clicking forward repeatedly. I clicked the skip button. Prior to rendering that final cross section, it gave me this error:

************** Exception Text **************
System.Runtime.InteropServices.SEHException: External component has thrown an exception.
   at Bentley.DTM.Element.DTMElementHandlerManager.IsDTMElement(ElemHandle* )
   at Bentley.DTM.Element.DTMElement.FromElemHandle(ElemHandle* elem)
   at Bentley.DTM.Element.DTMElementManager.FromElemHandle(ElemHandle* elem)
   at Bentley.Civil.Model.MSPlugIn.DTMHolderElementRef.get_DTM()
   at Bentley.Civil.Geometry.Model.DTMDataHolder.get_DTM()
   at Bentley.Civil.Geometry.Model.DTMEntity.get_DTM()
   at Bentley.Civil.Geometry.Model.Accessor.DtmEntity.DrapeLinear(ICollection`1 points)
   at uGeometricEntity._DrapeLinear(uGeometricEntity* , RefCountedPtr* , _dPoint3d* pts, Int32 numPoints)
   at rdLink_SetLastCorridorCrossSectionView(Int32 , Double* )
   at Bentley.Civil.RoadwayDesigner.RoadwayDesignerPlugin.DisplayCrossectioninView(CrossSectionDisplay crossSectionDisplay, Int32 viewIndex)
   at Bentley.Civil.RoadwayDesigner.RDManager.DisplayCrossectioninView(CrossSectionDisplay crossSectionDisplay, Int32 viewIndex)
   at Bentley.Civil.CadSystem.Microstation.MstnViewManager.LastStation(String unparsed)
   at Bentley.Internal.MicroStation.CoreHook.DispatchNoHandler(UInt32* argStack, UInt32 mysp, IntPtr pFunc)
   at Bentley.Internal.MicroStation.CoreHook.Dispatch(UInt32* argStack, UInt32 mysp, IntPtr pFunc)