Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/Billboard.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/Billboard.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/Billboard.cc	(revision 2161)
@@ -75,5 +75,6 @@
             {
                 this->billboard_.setBillboardSet(this->getScene()->getSceneManager(), this->material_, this->colour_, 1);
-                this->getNode()->attachObject(this->billboard_.getBillboardSet());
+                if (this->billboard_.getBillboardSet())
+                    this->getNode()->attachObject(this->billboard_.getBillboardSet());
                 this->billboard_.setVisible(this->isVisible());
             }
@@ -90,5 +91,6 @@
             {
                 this->billboard_.setBillboardSet(this->getScene()->getSceneManager(), this->material_, this->colour_, 1);
-                this->getNode()->attachObject(this->billboard_.getBillboardSet());
+                if (this->billboard_.getBillboardSet())
+                    this->getNode()->attachObject(this->billboard_.getBillboardSet());
                 this->billboard_.setVisible(this->isVisible());
             }
Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/Camera.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/Camera.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/Camera.cc	(revision 2161)
@@ -38,4 +38,5 @@
 #include <OgreViewport.h>
 
+#include "util/Exception.h"
 #include "core/CoreIncludes.h"
 #include "core/ConfigValueIncludes.h"
@@ -51,6 +52,6 @@
         RegisterObject(Camera);
 
-        assert(this->getScene());
-        assert(this->getScene()->getSceneManager());
+        if (!this->getScene() || !this->getScene()->getSceneManager())
+            throw AbortLoadingException("Can't create Camera, no scene or no scene manager given.");
 
         this->camera_ = this->getScene()->getSceneManager()->createCamera(getUniqueNumberString());
Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/ParticleEmitter.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/ParticleEmitter.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/ParticleEmitter.cc	(revision 2161)
@@ -37,4 +37,5 @@
 
 #include "tools/ParticleInterface.h"
+#include "util/Exception.h"
 #include "core/CoreIncludes.h"
 #include "core/XMLPort.h"
@@ -49,6 +50,6 @@
         RegisterObject(ParticleEmitter);
 
-        assert(this->getScene());
-        assert(this->getScene()->getSceneManager());
+        if (!this->getScene() || !this->getScene()->getSceneManager())
+            throw AbortLoadingException("Can't create Camera, no scene or no scene manager given.");
 
         this->particles_ = 0;
Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/WorldEntity.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/WorldEntity.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/WorldEntity.cc	(revision 2161)
@@ -36,4 +36,5 @@
 #include "core/XMLPort.h"
 #include "util/Convert.h"
+#include "util/Exception.h"
 
 #include "objects/Scene.h"
@@ -52,6 +53,6 @@
         RegisterObject(WorldEntity);
 
-        assert(this->getScene());
-        assert(this->getScene()->getRootSceneNode());
+        if (!this->getScene() || !this->getScene()->getRootSceneNode())
+            throw AbortLoadingException("Can't create WorldEntity, no scene or no root-scenenode given.");
 
         this->node_ = this->getScene()->getRootSceneNode()->createChildSceneNode();
Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/pawns/Spectator.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/pawns/Spectator.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/pawns/Spectator.cc	(revision 2161)
@@ -62,5 +62,6 @@
         this->greetingFlare_ = new BillboardSet();
         this->greetingFlare_->setBillboardSet(this->getScene()->getSceneManager(), "Examples/Flare", ColourValue(1.0, 1.0, 0.8), Vector3(0, 20, 0), 1);
-        this->getNode()->attachObject(this->greetingFlare_->getBillboardSet());
+        if (this->greetingFlare_->getBillboardSet())
+            this->getNode()->attachObject(this->greetingFlare_->getBillboardSet());
         this->greetingFlare_->setVisible(false);
         this->bGreetingFlareVisible_ = false;
@@ -76,5 +77,6 @@
             if (this->greetingFlare_)
             {
-                this->getNode()->detachObject(this->greetingFlare_->getBillboardSet());
+                if (this->greetingFlare_->getBillboardSet())
+                    this->getNode()->detachObject(this->greetingFlare_->getBillboardSet());
                 delete this->greetingFlare_;
             }
Index: code/branches/objecthierarchy/src/orxonox/objects/worldentities/triggers/Trigger.cc
===================================================================
--- code/branches/objecthierarchy/src/orxonox/objects/worldentities/triggers/Trigger.cc	(revision 2160)
+++ code/branches/objecthierarchy/src/orxonox/objects/worldentities/triggers/Trigger.cc	(revision 2161)
@@ -69,7 +69,9 @@
       this->debugBillboard_.setBillboardSet(this->getScene()->getSceneManager(), "Examples/Flare", ColourValue(1.0, 0.0, 0.0), 1);
       this->debugBillboard_.setVisible(false);
-    }
-
-    this->getNode()->attachObject(this->debugBillboard_.getBillboardSet());
+
+      if (this->debugBillboard_.getBillboardSet())
+        this->getNode()->attachObject(this->debugBillboard_.getBillboardSet());
+    }
+
     this->setObjectMode(0x0);
   }
@@ -310,5 +312,5 @@
   void Trigger::setBillboardColour(const ColourValue& colour)
   {
-    this->debugBillboard_.getBillboardSet()->getBillboard(0)->setColour(colour);
+    this->debugBillboard_.setColour(colour);
   }
 
