diff -r f636e2dcfb2c -r f3da1f26f949 client/js/paper-renderer.js
--- a/client/js/paper-renderer.js	Tue May 14 12:15:15 2013 +0200
+++ b/client/js/paper-renderer.js	Tue May 14 12:36:11 2013 +0200
@@ -319,7 +319,7 @@
     if (!_dontRedrawEdges) {
         Rkns._.each(this.project.get("edges").filter(function (ed) { return ((ed.to === this.model) || (ed.from === this.model));}), function(edge, index, list){
             var repr = this.renderer.getRepresentationByModel(edge);
-            if(repr != null && typeof repr.from_representation.paper_coords !== "undefined" && typeof repr.to_representation.paper_coords !== "undefined") {
+            if (repr && typeof repr.from_representation !== "undefined" && typeof repr.from_representation.paper_coords !== "undefined" && typeof repr.to_representation !== "undefined" && typeof repr.to_representation.paper_coords !== "undefined") {
                 repr.redraw();
             }
         }, this);
@@ -329,7 +329,7 @@
 
 Rkns.Renderer.Node.prototype.showImage = function() {
     if (typeof this.renderer.image_cache[this.img] === "undefined") {
-        var _image = new Image()
+        var _image = new Image();
         this.renderer.image_cache[this.img] = _image;
         _image.src = this.img;
     } else {
@@ -630,6 +630,13 @@
     this.from_representation = this.renderer.getRepresentationByModel(this.model.get("from"));
     this.to_representation = this.renderer.getRepresentationByModel(this.model.get("to"));
     if (!this.from_representation || !this.to_representation) {
+/*
+    console.log(
+            "Error on edge " + this.model.get("id")
+            + " from " + (this.model.get("from") ? this.model.get("from").get("id") : "<null>")
+            + " to " + (this.model.get("to") ? this.model.get("to").get("id") : "<null>")
+    );
+*/
         return;
     }
     var _p0a = this.from_representation.paper_coords,