diff --git a/Nef_3/include/CGAL/Nef_3/SNC_constructor.h b/Nef_3/include/CGAL/Nef_3/SNC_constructor.h
index ba1edc4efc1..cf2326bd199 100644
--- a/Nef_3/include/CGAL/Nef_3/SNC_constructor.h
+++ b/Nef_3/include/CGAL/Nef_3/SNC_constructor.h
@@ -1958,15 +1958,26 @@ public:
 	CGAL_NEF_TRACEN("");
       }
       
+      std::vector<Vertex_iterator> vertices_to_delete ;
       Vertex_iterator v;
       CGAL_forall_vertices(v, *this->sncp())
-	if(erase_vertex[v]) {
-	  CGAL_NEF_TRACEN("erase " << v->point());
-	  if(Infi_box::is_infibox_corner(v->point()))
-	    recreate.push_back(v->point());
-	  this->sncp()->delete_vertex(v);
-	  res = true;
-	}
+      {
+      	if(erase_vertex[v]) 
+        {
+      	  CGAL_NEF_TRACEN("erase " << v->point());
+      	  if(Infi_box::is_infibox_corner(v->point()))
+      	    recreate.push_back(v->point());
+          vertices_to_delete.push_back(v);
+      	  res = true;
+      	}
+      }
+      
+      for( typename std::vector<Vertex_iterator>::iterator vit = vertices_to_delete.begin()
+         ; vit != vertices_to_delete.end()
+         ; ++ vit 
+         )
+        this->sncp()->delete_vertex(*vit);
+         
       
       typename std::list<Point_3>::const_iterator pi;
       for(pi = recreate.begin(); pi != recreate.end(); ++pi)
diff --git a/Nef_3/include/CGAL/Nef_3/SNC_decorator.h b/Nef_3/include/CGAL/Nef_3/SNC_decorator.h
index f0367bdce4f..71b38e0178f 100644
--- a/Nef_3/include/CGAL/Nef_3/SNC_decorator.h
+++ b/Nef_3/include/CGAL/Nef_3/SNC_decorator.h
@@ -1459,8 +1459,8 @@ class SNC_decorator : public SNC_const_decorator<Map> {
 
       Shell_entry_iterator si;
       CGAL_forall_shells_of(si,voli) {
-	valid = valid && (si != Shell_entry_iterator() &&
-			  SFace_handle(si) != SFace_handle() && 
+	//valid = valid && (si != Shell_entry_iterator() &&
+	valid = valid && (SFace_handle(si) != SFace_handle() && 
 			  SFace_handle(si) != NULL);
 	valid = valid && (++count <= max);
       }
diff --git a/Nef_3/include/CGAL/Nef_3/SNC_io_parser.h b/Nef_3/include/CGAL/Nef_3/SNC_io_parser.h
index 345a08610fc..5238bc13f58 100644
--- a/Nef_3/include/CGAL/Nef_3/SNC_io_parser.h
+++ b/Nef_3/include/CGAL/Nef_3/SNC_io_parser.h
@@ -1079,13 +1079,13 @@ void SNC_io_parser<EW>::read()
   addInfiBox = (kernel_type == "standard" && Infi_box::extended_kernel());
 
   if(addInfiBox) {
-    Vertex_of.reserve(vn+8);
-    Edge_of.reserve(en+24);
-    Halffacet_of.reserve(fn+12);
-    Volume_of.reserve(cn+1);
-    SEdge_of.reserve(sen+48);
-    SLoop_of.reserve(sln);
-    SFace_of.reserve(sfn+16);
+    Vertex_of.resize(vn+8);
+    Edge_of.resize(en+24);
+    Halffacet_of.resize(fn+12);
+    Volume_of.resize(cn+1);
+    SEdge_of.resize(sen+48);
+    SLoop_of.resize(sln);
+    SFace_of.resize(sfn+16);
     for(i=0; i<vn+8; ++i)   Vertex_of[i] = this->sncp()->new_vertex_only();
     for(i=0; i<en+24; ++i)  Edge_of[i] = this->sncp()->new_halfedge_only();
     for(i=0; i<fn+12; ++i)  Halffacet_of[i] = this->sncp()->new_halffacet_only();
@@ -1095,13 +1095,13 @@ void SNC_io_parser<EW>::read()
     for(i=0; i<sfn+16; ++i) SFace_of[i] = this->sncp()->new_sface_only();
   }
   else {
-    Vertex_of.reserve(vn);
-    Edge_of.reserve(en);
-    Halffacet_of.reserve(fn);
-    Volume_of.reserve(cn);
-    SEdge_of.reserve(sen);
-    SLoop_of.reserve(sln);
-    SFace_of.reserve(sfn);
+    Vertex_of.resize(vn);
+    Edge_of.resize(en);
+    Halffacet_of.resize(fn);
+    Volume_of.resize(cn);
+    SEdge_of.resize(sen);
+    SLoop_of.resize(sln);
+    SFace_of.resize(sfn);
     for(i=0; i<vn; ++i)  Vertex_of[i] = this->sncp()->new_vertex_only();
     for(i=0; i<en; ++i)  Edge_of[i] = this->sncp()->new_halfedge_only();
     for(i=0; i<fn; ++i)  Halffacet_of[i] = this->sncp()->new_halffacet_only();
diff --git a/Nef_3/include/CGAL/Nef_3/SNC_simplify.h b/Nef_3/include/CGAL/Nef_3/SNC_simplify.h
index ebc4a94d7a2..e9b0e02e261 100644
--- a/Nef_3/include/CGAL/Nef_3/SNC_simplify.h
+++ b/Nef_3/include/CGAL/Nef_3/SNC_simplify.h
@@ -156,29 +156,36 @@ class SNC_simplify : public SNC_decorator<SNC_structure> {
       if(fc.is_shalfedge() ) {
 	SHalfedge_handle e(fc);
 	SHalfedge_around_facet_circulator u(e), eend(e);
-	CGAL_For_all(u, eend) {
-	  SFace_handle fu = u->incident_sface(), ftu = u->twin()->incident_sface();
-	  CGAL_NEF_TRACEN("sfUNION of "<<IO->index(fu)<<" & "<<IO->index(ftu));
-	  merge_sets( fu, ftu, hash, uf);
-	  SM_decorator SD(&*u->source()->source());
-	  CGAL_NEF_TRACEN("removing "<<IO->index(u)<<" & "<<IO->index(u->twin()));
-	  Halfedge_handle src(u->source()), tgt(u->target());
-	  if ( SD.is_closed_at_source(u) ) 
-	    SD.set_face( src, fu);
-	  if ( SD.is_closed_at_source( u->twin()) ) 
- 	    SD.set_face( tgt, fu);
+
+	//CGAL_For_all(u, eend) {
+   for ( bool _circ_loop_flag = ! ::CGAL::is_empty_range( u, eend); 
+         _circ_loop_flag; \
+         _circ_loop_flag = ( u != eend ) 
+       )
+   {
+  	  SFace_handle fu = u->incident_sface(), ftu = u->twin()->incident_sface();
+	    CGAL_NEF_TRACEN("sfUNION of "<<IO->index(fu)<<" & "<<IO->index(ftu));
+	    merge_sets( fu, ftu, hash, uf);
+	    SM_decorator SD(&*u->source()->source());
+	    CGAL_NEF_TRACEN("removing "<<IO->index(u)<<" & "<<IO->index(u->twin()));
+	    Halfedge_handle src(u->source()), tgt(u->target());
+	    if ( SD.is_closed_at_source(u) ) 
+	      SD.set_face( src, fu);
+	    if ( SD.is_closed_at_source( u->twin()) ) 
+ 	     SD.set_face( tgt, fu);
 	  /* TO VERIFY: does is_closed_at_source(u) imply is_isolated(src)?
 	     if it is true, the svertex face update is not necesary. */
-	  SD.delete_edge_pair(u); 
-	  if( SD.is_isolated(src))
-	    //	    SD.delete_vertex_only(src);
-	    SD.set_face(src,fu);
-	  SM_decorator SD2(&*tgt->source());
-	  if( SD2.is_isolated(tgt))
-	    // SD.delete_vertex_only(tgt);
-	    SD2.set_face(tgt,fu);
+     SHalfedge_around_facet_circulator next = u ;
+     ++ next ;
+	    SD.delete_edge_pair(u); 
+	    if( SD.is_isolated(src))
+  	    SD.set_face(src,fu);
+  	  SM_decorator SD2(&*tgt->source());
+	    if( SD2.is_isolated(tgt))
+  	    SD2.set_face(tgt,fu);
+     u = next ;
 	  /* TO VERIFY: can both svertices be isolated at the same time? */
-      }
+   }
       }
       else if(fc.is_shalfloop()) {
 	SHalfloop_handle l(fc);
@@ -458,9 +465,10 @@ class SNC_simplify : public SNC_decorator<SNC_structure> {
      CGAL_NEF_TRACEN("s2 = " << IO->index(s2));
      if( s1 == s2) {
        CGAL_NEF_TRACEN(IO->index(s1)<<'('<<IO->index(s2->twin())<<") to sloop");
+       Halffacet_handle facet = s1->facet();
        SD.convert_edge_to_loop(s1);
        CGAL_assertion(SD.shalfloop() != SHalfloop_handle());
-       D.add_sloop_to_facet( SD.shalfloop(), s1->facet());
+       D.add_sloop_to_facet( SD.shalfloop(), facet);
        CGAL_NEF_TRACEN(IO->index(s2)<<" removed");
      }
      else {
diff --git a/Nef_3/include/CGAL/Nef_3/SNC_structure.h b/Nef_3/include/CGAL/Nef_3/SNC_structure.h
index f218e18a5d9..9494b5a29d4 100644
--- a/Nef_3/include/CGAL/Nef_3/SNC_structure.h
+++ b/Nef_3/include/CGAL/Nef_3/SNC_structure.h
@@ -40,6 +40,9 @@
 #include <CGAL/Nef_2/debug.h>
 #include <CGAL/Nef_2/Object_index.h>
 
+#include <boost/optional.hpp>
+#include <boost/none.hpp>
+
 CGAL_BEGIN_NAMESPACE
 
 template <typename HE>
@@ -691,13 +694,13 @@ public:
   expensive operation.}*/
 
   SNC_structure() : 
-    boundary_item_(undef_), sm_boundary_item_(undef_),
+    boundary_item_(boost::none), sm_boundary_item_(boost::none),
     vertices_(), halfedges_(), halffacets_(), volumes_(),
     shalfedges_(), shalfloops_(), sfaces_() {}
   ~SNC_structure() { CGAL_NEF_TRACEN("~SNC_structure: clearing "<<this); clear(); }
 
   SNC_structure(const Self& D) : 
-    boundary_item_(undef_), sm_boundary_item_(undef_),
+    boundary_item_(boost::none), sm_boundary_item_(boost::none),
     vertices_(D.vertices_), halfedges_(D.halfedges_), 
     halffacets_(D.halffacets_), volumes_(D.volumes_),
     shalfedges_(D.shalfedges_), shalfloops_(D.shalfloops_), 
@@ -708,8 +711,8 @@ public:
     if ( this == &D ) 
       return *this;
     clear();
-    boundary_item_.clear(undef_);
-    sm_boundary_item_.clear(undef_);
+    boundary_item_.clear(boost::none);
+    sm_boundary_item_.clear(boost::none);
     vertices_ = D.vertices_;
     halfedges_ = D.halfedges_;
     halffacets_ = D.halffacets_;
@@ -722,17 +725,17 @@ public:
   }
 
   void clear_boundary() {
-    boundary_item_.clear(undef_);
-    sm_boundary_item_.clear(undef_);
+    boundary_item_.clear(boost::none);
+    sm_boundary_item_.clear(boost::none);
   }
 
   void clear_snc_boundary() {
-    boundary_item_.clear(undef_);
+    boundary_item_.clear(boost::none);
   }
 
   void clear() { 
-    boundary_item_.clear(undef_);
-    sm_boundary_item_.clear(undef_);
+    boundary_item_.clear(boost::none);
+    sm_boundary_item_.clear(boost::none);
     vertices_.destroy();
     halfedges_.destroy();
     halffacets_.destroy();
@@ -744,17 +747,17 @@ public:
 
   template <typename H>
   bool is_boundary_object(H h) 
-  { return boundary_item_[h]!=undef_; }
+  { return boundary_item_[h]!=boost::none; }
   template <typename H>
   bool is_sm_boundary_object(H h) 
-  { return sm_boundary_item_[h]!=undef_; }
+  { return sm_boundary_item_[h]!=boost::none; }
 
   template <typename H>
   Object_iterator& boundary_item(H h)
-  { return boundary_item_[h]; }
+  { return *boundary_item_[h]; }
   template <typename H>
   Object_iterator& sm_boundary_item(H h)
-  { return sm_boundary_item_[h]; }
+  { return *sm_boundary_item_[h]; }
 
   template <typename H>
   void store_boundary_item(H h, Object_iterator o)
@@ -765,12 +768,12 @@ public:
 
   template <typename H>
   void undef_boundary_item(H h)
-  { CGAL_assertion(boundary_item_[h]!=undef_);
-    boundary_item_[h] = undef_; }
+  { CGAL_assertion(boundary_item_[h]!=boost::none);
+    boundary_item_[h] = boost::none; }
   template <typename H>
   void undef_sm_boundary_item(H h)
-  { CGAL_assertion(sm_boundary_item_[h]!=undef_);
-    sm_boundary_item_[h] = undef_; }
+  { CGAL_assertion(sm_boundary_item_[h]!=boost::none);
+    sm_boundary_item_[h] = boost::none; }
 
   void reset_iterator_hash(Object_iterator it)
   { SVertex_handle sv;
@@ -1335,9 +1338,11 @@ public:
 
 protected:
   void pointer_update(const Self& D);
-  static Object_iterator              undef_;
-  Generic_handle_map<Object_iterator> boundary_item_;
-  Generic_handle_map<Object_iterator> sm_boundary_item_;
+  
+  typedef boost::optional<Object_iterator> Optional_object_iterator ;
+  
+  Generic_handle_map<Optional_object_iterator> boundary_item_;
+  Generic_handle_map<Optional_object_iterator> sm_boundary_item_;
 
   Vertex_list    vertices_;
   Halfedge_list  halfedges_;
@@ -1483,10 +1488,5 @@ pointer_update(const SNC_structure<Kernel,Items,Mark>& D)
   }
 }
 
-template <typename Kernel, typename Items, typename Mark> 
-typename SNC_structure<Kernel, Items, Mark>::Object_iterator
-SNC_structure<Kernel,Items,Mark>::undef_;
-
-
 CGAL_END_NAMESPACE
 #endif // CGAL_SNC_STRUCTURE_H