diff -r cbfbd0f7135b -r 0fa72713501d PLCControler.py
--- a/PLCControler.py	Tue Apr 19 14:53:08 2011 +0200
+++ b/PLCControler.py	Tue Apr 19 14:57:01 2011 +0200
@@ -194,7 +194,7 @@
     # Reset PLCControler internal variables
     def Reset(self):
         self.Project = None
-        self.ProjectBufferEnabled = False
+        self.ProjectBufferEnabled = True
         self.ProjectBuffer = None
         self.ProjectSaved = True
         self.Buffering = False
@@ -2663,7 +2663,7 @@
 
     def CreateProjectBuffer(self, saved):
         if self.ProjectBufferEnabled:
-            self.ProjectBuffer = UndoBuffer(self.Copy(self.Project), saved)
+            self.ProjectBuffer = UndoBuffer(cPickle.dumps(self.Project), saved)
         else:
             self.ProjectBuffer = None
             self.ProjectSaved = saved
@@ -2682,20 +2682,19 @@
 
     def BufferProject(self):
         if self.ProjectBuffer is not None:
-            self.ProjectBuffer.Buffering(self.Copy(self.Project))
+            self.ProjectBuffer.Buffering(cPickle.dumps(self.Project))
         else:
             self.ProjectSaved = False
 
     def StartBuffering(self):
         if self.ProjectBuffer is not None:
-            self.ProjectBuffer.Buffering(self.Project)
             self.Buffering = True
         else:
             self.ProjectSaved = False
         
     def EndBuffering(self):
         if self.ProjectBuffer is not None and self.Buffering:
-            self.Project = self.Copy(self.Project)
+            self.ProjectBuffer.Buffering(cPickle.dumps(self.Project))
             self.Buffering = False
 
     def MarkProjectAsSaved(self):
@@ -2707,21 +2706,24 @@
     # Return if project is saved
     def ProjectIsSaved(self):
         if self.ProjectBuffer is not None:
-            return self.ProjectBuffer.IsCurrentSaved()
+            return self.ProjectBuffer.IsCurrentSaved() and not self.Buffering
         else:
             return self.ProjectSaved
 
     def LoadPrevious(self):
         if self.ProjectBuffer is not None:
-            self.Project = self.Copy(self.ProjectBuffer.Previous())
+            if self.Buffering:
+                self.Project = cPickle.loads(self.ProjectBuffer.Current())
+            else:
+                self.Project = cPickle.loads(self.ProjectBuffer.Previous())
     
     def LoadNext(self):
         if self.ProjectBuffer is not None:
-            self.Project = self.Copy(self.ProjectBuffer.Next())
+            self.Project = cPickle.loads(self.ProjectBuffer.Next())
     
     def GetBufferState(self):
         if self.ProjectBuffer is not None:
             first = self.ProjectBuffer.IsFirst()
-            last = self.ProjectBuffer.IsLast()
+            last = self.ProjectBuffer.IsLast() and not self.Buffering
             return not first, not last
         return False, False