.NET framework error: Bentley.Civil.Objects.ModelLightweightClass.SetList

This is the contents of the error:

************** Exception Text **************
System.InvalidCastException: Unable to cast object of type 'Bentley.Civil.Objects.Engine.ObjectList' to type 'Bentley.Civil.Objects.IListWithProperties'.
   at Bentley.Civil.Objects.ModelLightweightClass.SetList(Object obj, Object list, DirectedRelationshipDescriptor relDescr)
   at Bentley.Civil.Objects.Engine.Instance.BindObjectListsToCLRObject(Object obj, Boolean fromPersistence)
   at Bentley.Civil.Objects.Engine.Instance.StartTracking()
   at Bentley.Civil.Objects.Engine.ObjectSpace.StartTracking(Object obj, ObjectKeyInternal ecKey)
   at Bentley.Civil.Objects.Engine.ObjectSpace.CheckAndStartTracking(Object obj)
   at Bentley.Civil.Objects.Engine.Instance.AddRelation(DirectedRelationship rel, Boolean fromPersistence)
   at Bentley.Civil.Objects.Engine.Instance.BindObjectListsToCLRObject(Object obj, Boolean fromPersistence)
   at Bentley.Civil.Objects.Engine.Instance.StartTracking()
   at Bentley.Civil.Objects.Engine.ObjectSpace.StartTracking(Object obj, ObjectKeyInternal ecKey)
   at Bentley.Civil.Objects.Engine.Instance.AddRelation(DirectedRelationship rel, Boolean fromPersistence)
   at Bentley.Civil.Objects.Engine.Instance.BindObjectListsToCLRObject(Object obj, Boolean fromPersistence)
   at Bentley.Civil.Objects.Engine.Instance.StartTracking()
   at Bentley.Civil.Objects.Engine.ObjectSpace.StartTracking(Object obj, ObjectKeyInternal ecKey)
   at Bentley.Civil.Objects.Engine.ObjectSpace.CheckAndStartTracking(Object obj)
   at Bentley.Civil.Objects.Engine.ObjectSpace.PersistChanges(Object obj, PersistDepth persistDepth)
   at Bentley.Civil.Objects.Engine.ObjectSpace.Bentley.Civil.Objects.IObjectTracker.PersistChanges(Object obj)
   at Bentley.Civil.Objects.Encapsulation.ObjectSpaceEncapsulation.PersistChanges(Object obj)
   at Bentley.Civil.Geometry.Model.DTMEntitySource.RestoreDTM(String tempFile, IObjectSpace objectSpace)
   at Bentley.Civil.Commands.DTM.DTMUpdateSources.UpdateSource(ProgressController controller, DTMEntitySource source)
   at Bentley.Civil.Commands.DTM.DTMUpdateSources.OnInstall()
   at Bentley.Civil.Geometry.Command.GeometryCommand.DoOnInstall()
   at Bentley.Civil.Geometry.Command.GeometryCommand.GeometryManagedCommand.OnInstall()
   at Bentley.Civil.UI.Commands.ManagedCommand.Install(Boolean forDrag, Object manipulatedObject)
   at Bentley.Civil.UI.Commands.ManagedCommand.Install()
   at Bentley.Civil.Geometry.Command.GeometryCommand.GeometryManagedCommand.BaseInstall(Boolean forDrag, Object manipulatedObject)
   at Bentley.Civil.Geometry.Command.GeometryCommand.Install()
   at Bentley.Civil.Geometry.Command.GeometryCommand.GeometryManagedCommand.Install()
   at Bentley.Civil.UI.Commands.ManagedCommand.LaunchManagedComand(String keyIn, String unparsedParams)
   at Bentley.Civil.Commands.Addin.DTMUpdateSources(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)

This occurred as I right-clicked a terrain model and then clicked to refresh from source. The only source is a set of spot shots.

Sometimes errors allow you to work through them (although at that point something is definitely broken). In this case, the processing window looks like it's progressing but then the error log submission screen shows up.

Using Geopak SS4 .845.