Index: /trunk/sources/HeuristicLab.Encodings.BinaryVectorEncoding/3.3/Crossovers/MultiBinaryVectorCrossover.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.BinaryVectorEncoding/3.3/Crossovers/MultiBinaryVectorCrossover.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.BinaryVectorEncoding/3.3/Crossovers/MultiBinaryVectorCrossover.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -76,4 +77,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one binary vector crossover to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Encodings.IntegerVectorEncoding/3.3/Crossovers/MultiIntegerVectorCrossover.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.IntegerVectorEncoding/3.3/Crossovers/MultiIntegerVectorCrossover.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.IntegerVectorEncoding/3.3/Crossovers/MultiIntegerVectorCrossover.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -76,4 +77,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one integer vector crossover to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Crossovers/MultiPermutationCrossover.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Crossovers/MultiPermutationCrossover.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Crossovers/MultiPermutationCrossover.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -76,4 +77,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one permutation crossover to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Manipulators/MultiPermutationManipulator.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Manipulators/MultiPermutationManipulator.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Manipulators/MultiPermutationManipulator.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -68,4 +69,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one permutation manipulator to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Crossovers/MultiRealVectorCrossover.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Crossovers/MultiRealVectorCrossover.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Crossovers/MultiRealVectorCrossover.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -81,4 +82,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one real vector crossover to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Manipulators/MultiRealVectorManipulator.cs
===================================================================
--- /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Manipulators/MultiRealVectorManipulator.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Encodings.RealVectorEncoding/3.3/Manipulators/MultiRealVectorManipulator.cs	(revision 3527)
@@ -20,4 +20,5 @@
 #endregion
 
+using System;
 using System.Linq;
 using HeuristicLab.Collections;
@@ -74,4 +75,9 @@
       }
     }
+
+    public override IOperation Apply() {
+      if (Operators.Count == 0) throw new InvalidOperationException(Name + ": Please add at least one real vector manipulator to choose from.");
+      return base.Apply();
+    }
   }
 }
Index: /trunk/sources/HeuristicLab.Operators/3.3/StochasticMultiOperator.cs
===================================================================
--- /trunk/sources/HeuristicLab.Operators/3.3/StochasticMultiOperator.cs	(revision 3526)
+++ /trunk/sources/HeuristicLab.Operators/3.3/StochasticMultiOperator.cs	(revision 3527)
@@ -34,5 +34,5 @@
   /// Base class for stochastic multi operators.
   /// </summary>
-  [Item("StochasticMultiOperator", "Base class for stochastic multi operators.")]
+  [Item("StochasticMultiOperator<T>", "Base class for stochastic multi operators.")]
   [StorableClass]
   public abstract class StochasticMultiOperator<T> : MultiOperator<T> where T : class, IOperator {
@@ -58,5 +58,5 @@
     protected StochasticMultiOperator(bool deserializing) : base(deserializing) { }
     /// <summary>
-    /// Initializes a new instance of <see cref="StochasticMultiBranch"/> with two parameters
+    /// Initializes a new instance of <see cref="StochasticMultiOperator"/> with two parameters
     /// (<c>Probabilities</c> and <c>Random</c>).
     /// </summary>
@@ -119,5 +119,5 @@
       DoubleArray probabilities = ProbabilitiesParameter.ActualValue;
       if(probabilities.Length != Operators.Count) {
-        throw new InvalidOperationException("MultiCrossover: The list of probabilities has to match the number of operators");
+        throw new InvalidOperationException(Name + ": The list of probabilities has to match the number of operators");
       }
       double sum = 0;
