SimObject::deleteObject() fails

When I call shape.deleteObject() [shape is a TSStatic], TSE crashes when it executes "delete this":

void SimObject::deleteObject()
{
	AssertFatal(mFlags.test(Added),
		"SimObject::deleteObject: Object not registered.");
	AssertFatal(!isDeleted(),"SimManager::deleteObject: "
		"Object has already been deleted");
	AssertFatal(!isRemoved(),"SimManager::deleteObject: "
		"Object in the process of being removed");
	mFlags.set(Deleted);

   unregisterObject();
   delete this;
}

However, if I don't call shape.deleteObject(), I get an assert:

SimObject::object missing call to SimObject::onRemove

The object is a child class of WheeledVehicle, and onRemove() has these statements:

void SimChild2::onRemove()
{

	shape.removeFromScene();
	shape.deleteObject();

	Parent::onRemove();
}

But of course deleteObject() crashes TSE. What is the problem?

Note: everything runs fine in the release mode (if I comment out the deleteObject(), but am probably leaking memory/resources).