diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/ITemplateModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/ITemplateModel.java
index f50f9852e..ee1430474 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/ITemplateModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/ITemplateModel.java
@@ -37,6 +37,8 @@ public interface ITemplateModel {
 
     public interface IOnFinished {
         public void onWithoutErrorFinish();
+
+        public void errorHappened(Exception exceptionHappened);
     }
 
     void setScenario(String loginName, Scenario scenario,
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateController.java
index 6798ba0e9..e61215cda 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateController.java
@@ -20,9 +20,13 @@
 
 package org.navalplanner.web.common;
 
+import static org.navalplanner.web.I18nHelper._;
+
 import java.util.Collections;
 import java.util.List;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.navalplanner.business.scenarios.IScenarioManager;
 import org.navalplanner.business.scenarios.entities.Scenario;
 import org.navalplanner.web.common.ITemplateModel.IOnFinished;
@@ -46,6 +50,8 @@ import org.zkoss.zul.Window;
 @Scope(BeanDefinition.SCOPE_PROTOTYPE)
 public class TemplateController extends GenericForwardComposer {
 
+    private static final Log LOG = LogFactory.getLog(TemplateController.class);
+
     @Autowired
     private ITemplateModel templateModel;
 
@@ -54,10 +60,14 @@ public class TemplateController extends GenericForwardComposer {
 
     private Window window;
 
+    private IMessagesForUser windowMessages;
+
     @Override
     public void doAfterCompose(Component comp) throws Exception {
         super.doAfterCompose(comp);
         window = (Window) comp.getFellow("changeScenarioWindow");
+        windowMessages = new MessagesForUser(window
+                .getFellow("messagesContainer"));
     }
 
     public Scenario getScenario() {
@@ -89,6 +99,15 @@ public class TemplateController extends GenericForwardComposer {
                         window.setVisible(false);
                         Executions.sendRedirect("/");
                     }
+
+                    @Override
+                    public void errorHappened(Exception exceptionHappened) {
+                        LOG.error("error doing reassignation",
+                                exceptionHappened);
+                        windowMessages.showMessage(Level.ERROR, _(
+                                "error doing reassignation: {0}",
+                                exceptionHappened));
+                    }
                 });
     }
 
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateModel.java
index 7a6b7c2f5..2d794d2db 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/common/TemplateModel.java
@@ -423,6 +423,7 @@ public class TemplateModel implements ITemplateModel {
             @Override
             public void doOperation(
                     final IDesktopUpdatesEmitter<IDesktopUpdate> desktopUpdateEmitter) {
+                Exception exceptionHappened = null;
                 try {
                     transactionService
                             .runOnTransaction(new IOnTransaction<Void>() {
@@ -433,17 +434,25 @@ public class TemplateModel implements ITemplateModel {
                                     return null;
                                 }
                             });
+                } catch (Exception e) {
+                    exceptionHappened = e;
                 } finally {
                     desktopUpdateEmitter.doUpdate(showEnd());
                 }
-                desktopUpdateEmitter.doUpdate(executeFinish(onFinish));
+                if (exceptionHappened == null) {
+                    desktopUpdateEmitter.doUpdate(notifySuccess(onFinish));
+                } else {
+                    desktopUpdateEmitter.doUpdate(notifyException(onFinish,
+                            exceptionHappened));
+                }
             }
+
         };
         LongOperationFeedback.progressive(desktop, LongOperationFeedback
                 .withAsyncUpates(reassignations));
     }
 
-    private IDesktopUpdate executeFinish(
+    private IDesktopUpdate notifySuccess(
             final IOnFinished onFinish) {
         return new IDesktopUpdate() {
 
@@ -454,6 +463,16 @@ public class TemplateModel implements ITemplateModel {
         };
     }
 
+    private IDesktopUpdate notifyException(final IOnFinished onFinish,
+            final Exception exceptionHappened) {
+        return new IDesktopUpdate() {
+
+            @Override
+            public void doUpdate() {
+                onFinish.errorHappened(exceptionHappened);
+            }
+        };
+    }
 
     private void doReassignations(Scenario scenario,
             IDesktopUpdatesEmitter<IDesktopUpdate> emitter) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/scenarios/ScenarioCRUDController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/scenarios/ScenarioCRUDController.java
index 2f93344d3..4174a05e1 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/scenarios/ScenarioCRUDController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/scenarios/ScenarioCRUDController.java
@@ -26,6 +26,8 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.navalplanner.business.common.exceptions.ValidationException;
 import org.navalplanner.business.orders.entities.Order;
 import org.navalplanner.business.scenarios.IScenarioManager;
@@ -62,6 +64,9 @@ import org.zkoss.zul.api.Window;
  */
 public class ScenarioCRUDController extends GenericForwardComposer {
 
+    private static final Log LOG = LogFactory
+            .getLog(ScenarioCRUDController.class);
+
     @Autowired
     private IScenarioModel scenarioModel;
 
@@ -234,8 +239,15 @@ public class ScenarioCRUDController extends GenericForwardComposer {
                                             Executions
                                                     .sendRedirect("/scenarios/scenarios.zul");
                                         }
+
+                                        @Override
+                                        public void errorHappened(
+                                                Exception exceptionHappened) {
+                                            errorHappenedDoingReassignation(exceptionHappened);
+                                        }
                                     });
                         }
+
                     });
             if (isCurrentScenario) {
                 connectButton.setDisabled(true);
@@ -252,6 +264,12 @@ public class ScenarioCRUDController extends GenericForwardComposer {
 
     }
 
+    private void errorHappenedDoingReassignation(Exception exceptionHappened) {
+        LOG.error("error happened doing reassignation", exceptionHappened);
+        messagesForUser.showMessage(Level.ERROR, _(
+                "error doing reassignation: {0}", exceptionHappened));
+    }
+
     public Set<Order> getOrders() {
         Scenario scenario = scenarioModel.getScenario();
         if (scenario == null) {
diff --git a/navalplanner-webapp/src/main/webapp/common/layout/template.zul b/navalplanner-webapp/src/main/webapp/common/layout/template.zul
index 0281dbfbb..13e03a07b 100644
--- a/navalplanner-webapp/src/main/webapp/common/layout/template.zul
+++ b/navalplanner-webapp/src/main/webapp/common/layout/template.zul
@@ -70,6 +70,7 @@
                     label="${templateCtrl.scenario.name}" />
                 <window id="changeScenarioWindow" visible="false"
                     title="${i18n:_('Change scenario')}">
+                    <div id="messagesContainer" />
                     <grid>
                         <rows>
                             <row>