diff --git a/AMDiS/src/ResidualEstimator.cc b/AMDiS/src/ResidualEstimator.cc
index bf8ae05be00e1016b4db4026746fda94b7a72b27..1b1af2bac3138546ca38cb69557e08d728d80e8e 100644
--- a/AMDiS/src/ResidualEstimator.cc
+++ b/AMDiS/src/ResidualEstimator.cc
@@ -218,7 +218,7 @@ namespace AMDiS {
 	}
       }
 	
-      if (timestep) {
+      if (timestep && uhOld[system]) {
 	TEST_EXIT_DBG(uhOld[system])("no uhOld\n");
 	uhOld[system]->getLocalVector(el, uhOldEl[system]);
   
@@ -278,16 +278,14 @@ namespace AMDiS {
 
     // add integral over r square
     val = 0.0;
-    for (int iq = 0; iq < nPoints; iq++) {
+    for (int iq = 0; iq < nPoints; iq++)
       val += quad->getWeight(iq) * riq[iq] * riq[iq];
-    }
    
-    if (timestep != 0.0 || norm == NO_NORM || norm == L2_NORM) {
+    if (timestep != 0.0 || norm == NO_NORM || norm == L2_NORM)
       val = C0 * h2 * h2 * det * val;
-    } else {
+    else
       val = C0 * h2 * det * val;
-    }
-
+    
     est_el += val;
 
     // ===== jump residuals 
diff --git a/AMDiS/src/Serializer.h b/AMDiS/src/Serializer.h
index 49840bec49095211544fb80de53e7558a1ee01fa..37404ab1d504682fe9b7ebe21d7860bf809caf8b 100644
--- a/AMDiS/src/Serializer.h
+++ b/AMDiS/src/Serializer.h
@@ -1,4 +1,4 @@
-
+// ============================================================================
 // ==                                                                        ==
 // == AMDiS - Adaptive multidimensional simulations                          ==
 // ==                                                                        ==
@@ -34,8 +34,6 @@ namespace AMDiS {
   class Serializer : public FileWriterInterface
   {
   public:
-    MEMORY_MANAGED(Serializer);
-
     Serializer(ProblemType *problem) 
       : name_(""), 
 	problem_(problem), 
@@ -61,13 +59,13 @@ namespace AMDiS {
 
       timestepNumber_++;
       timestepNumber_ %= tsModulo_;
-      if ((timestepNumber_ != 0) && !force) {
+      if ((timestepNumber_ != 0) && !force)
 	return;
-      }
 
       TEST_EXIT(adaptInfo)("No AdaptInfo\n");
 
       std::ofstream out(name_.c_str());
+      TEST_EXIT(out.is_open())("Cannot open serialization file!\n");
       problem_->serialize(out);
       adaptInfo->serialize(out);
       out.close();
@@ -82,24 +80,16 @@ namespace AMDiS {
     }
 
   protected:
-    /** \brief
-     * Name of file to which the problem is serialized.
-     */
+    /// Name of file to which the problem is serialized.
     std::string name_;
 
-    /** \brief
-     * Pointer to the problem.
-     */
+    /// Pointer to the problem.
     ProblemType *problem_;
 
-    /** \brief
-     * The problem is serialized every tsModulo-th timestep.
-     */
+    /// The problem is serialized every tsModulo-th timestep.
     int tsModulo_;
 
-    /** \brief
-     * Current timestep number.
-     */
+    /// Current timestep number.
     int timestepNumber_;
   };