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 793243)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/LocalItemStateManager.java	Fri Oct 16 16:03:36 CEST 2009
@@ -407,11 +407,21 @@
             try {
                 local = changeLog.get(created.getId());
                 if (local != null) {
+                    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);
-                }
+                            // 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/ItemManager.java
===================================================================
--- jackrabbit-core/src/main/java/org/apache/jackrabbit/core/ItemManager.java	(revision 817192)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/ItemManager.java	Fri Oct 16 16:03:36 CEST 2009
@@ -1055,7 +1055,6 @@
             itemDestroyed(destroyed.getId(), data);
 
             data.setStatus(ItemImpl.STATUS_DESTROYED);
-            data.setState(null);
         }
     }
 
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 816343)
+++ jackrabbit-core/src/main/java/org/apache/jackrabbit/core/state/SharedItemStateManager.java	Fri Oct 16 16:34:16 CEST 2009
@@ -626,7 +626,7 @@
                                                         parent.getNodeTypeName(),
                                                         parent.getMixinTypeNames());
                                                 QNodeDefinition def = ent.getApplicableChildNodeDef(name, ns.getNodeTypeName(), ntReg);
-                                                return def != null ? def.allowsSameNameSiblings() : false;
+                                                return def != null && def.allowsSameNameSiblings();
                                             } catch (Exception e) {
                                                 log.warn("Unable to get node definition", e);
                                                 return false;
@@ -668,6 +668,14 @@
                     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());
                 }
Index: jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java
===================================================================
--- jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java	(revision 809527)
+++ jackrabbit-core/src/test/java/org/apache/jackrabbit/core/ConcurrentImportTest.java	Fri Oct 16 16:03:36 CEST 2009
@@ -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);
@@ -203,4 +207,4 @@
 
     }
 
-}
\ No newline at end of file
+}