Index: jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java
===================================================================
--- jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java	(revision 813472)
+++ jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java	(working copy)
@@ -112,6 +112,10 @@
                     log.println("Error: " + e);
                     log.flush();
                     throw e;
+                } catch (Exception e) {
+                    log.println("Unexpected error: " + e);
+                    log.flush();
+                    throw new RepositoryException(e);
                 }
             }
         }, CONCURRENCY, "/" + testPath);
Index: jackrabbit-core/src/main/java/org/apache/jackrabbit/core/ItemManager.java
===================================================================
--- jackrabbit-core/src/main/java/org/apache/jackrabbit/core/ItemManager.java	(revision 813472)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/ItemManager.java	(working copy)
@@ -998,7 +998,6 @@
             itemDestroyed(destroyed.getId(), data);
 
             data.setStatus(ItemImpl.STATUS_DESTROYED);
-            data.setState(null);
         }
     }
 
Index: jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/LocalItemStateManager.java
===================================================================
--- jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/LocalItemStateManager.java	(revision 813472)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/LocalItemStateManager.java	(working copy)
@@ -407,10 +407,20 @@
             try {
                 local = changeLog.get(created.getId());
                 if (local != null) {
-                    // underlying state has been permanently created
-                    local.pull();
-                    local.setStatus(ItemState.STATUS_EXISTING);
-                    cache.cache(local);
+                    if (local.isNode() && local.getOverlayedState() != created) {
+                        // mid-air collision of concurrent node state creation
+                        // with same id (JCR-2272)
+                        if (local.getStatus() == ItemState.STATUS_NEW) {
+                            local.setStatus(ItemState.STATUS_STALE_MODIFIED);
+                        }
+                    } else {
+                        if (local.getOverlayedState() == created) {
+                            // underlying state has been permanently created
+                            local.pull();
+                            local.setStatus(ItemState.STATUS_EXISTING);
+                            cache.cache(local);
+                        }
+                    }
                 }
             } catch (NoSuchItemStateException e) {
                 /* ignore */
Index: jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/SharedItemStateManager.java
===================================================================
--- jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/SharedItemStateManager.java	(revision 813472)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/SharedItemStateManager.java	(working copy)
@@ -20,6 +20,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Set;
+import java.util.Calendar;
 
 import javax.jcr.PropertyType;
 import javax.jcr.ReferentialIntegrityException;
@@ -48,6 +49,7 @@
 import org.apache.jackrabbit.core.virtual.VirtualItemStateProvider;
 import org.apache.jackrabbit.spi.Name;
 import org.apache.jackrabbit.spi.commons.name.NameConstants;
+import org.apache.jackrabbit.JcrConstants;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -632,7 +634,7 @@
                                                 return false;
                                             }
                                             NodeDef def = ntReg.getNodeDef(ns.getDefinitionId());
-                                            return def != null ? def.allowsSameNameSiblings() : false;
+                                            return def != null && def.allowsSameNameSiblings();
                                         }
                                     };
 
@@ -661,6 +663,14 @@
                     shared.deleted(state.getOverlayedState());
                 }
                 for (ItemState state : local.addedStates()) {
+                    if (state.isNode() && state.getStatus() != ItemState.STATUS_NEW) {
+                        // another node with same id had been created
+                        // in the meantime, probably caused by mid-air collision
+                        // of concurrent versioning operations (JCR-2272)
+                        String msg = state.getId() + " has been created externally";
+                        log.debug(msg);
+                        throw new StaleItemStateException(msg);
+                    }
                     state.connect(createInstance(state));
                     shared.added(state.getOverlayedState());
                 }