diff --git a/lib/Doctrine/ORM/ORMException.php b/lib/Doctrine/ORM/ORMException.php
index 7f541cf7a..aa0233064 100644
--- a/lib/Doctrine/ORM/ORMException.php
+++ b/lib/Doctrine/ORM/ORMException.php
@@ -20,4 +20,14 @@ class ORMException extends \Exception
                 . " detected in collection '" . $assoc->sourceFieldName . "' during flush."
                 . " Remove deleted entities from collections.");
     }
+    
+    public static function invalidEntityState($state)
+    {
+        return new self("Invalid entity state: $state.");
+    }
+    
+    public static function detachedEntityCannotBeRemoved()
+    {
+        return new self("A detached entity can not be removed.");
+    }
 }
diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 558ee2050..3eaa83cc7 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -854,13 +854,13 @@ class UnitOfWork implements PropertyChangedListener
         $oid = spl_object_hash($entity);
 
         if (isset($this->_entityUpdates[$oid])) {
-            throw DoctrineException::dirtyObjectCannotBeRegisteredAsNew();
+            throw new \InvalidArgumentException("Dirty entity can not be scheduled for insertion.");
         }
         if (isset($this->_entityDeletions[$oid])) {
-            throw DoctrineException::removedObjectCannotBeRegisteredAsNew();
+            throw new \InvalidArgumentException("Removed entity can not be scheduled for insertion.");
         }
         if (isset($this->_entityInsertions[$oid])) {
-            throw DoctrineException::objectAlreadyRegisteredAsNew();
+            throw new \InvalidArgumentException("Entity can not be scheduled for insertion twice.");
         }
 
         $this->_entityInsertions[$oid] = $entity;
@@ -890,10 +890,10 @@ class UnitOfWork implements PropertyChangedListener
     {
         $oid = spl_object_hash($entity);
         if ( ! isset($this->_entityIdentifiers[$oid])) {
-            throw DoctrineException::entityWithoutIdentityCannotBeRegisteredAsDirty();
+            throw new \InvalidArgumentException("Entity has no identity.");
         }
         if (isset($this->_entityDeletions[$oid])) {
-            throw DoctrineException::removedObjectCannotBeRegisteredAsDirty();
+            throw new \InvalidArgumentException("Entity is removed.");
         }
 
         if ( ! isset($this->_entityUpdates[$oid]) && ! isset($this->_entityInsertions[$oid])) {
@@ -1009,7 +1009,7 @@ class UnitOfWork implements PropertyChangedListener
         $classMetadata = $this->_em->getClassMetadata(get_class($entity));
         $idHash = implode(' ', $this->_entityIdentifiers[spl_object_hash($entity)]);
         if ($idHash === '') {
-            throw DoctrineException::entityMustHaveIdentityToBeAddedToIdentityMap($entity);
+            throw new \InvalidArgumentException("The given entity has no identity.");
         }
         $className = $classMetadata->rootEntityName;
         if (isset($this->_identityMap[$className][$idHash])) {
@@ -1072,7 +1072,7 @@ class UnitOfWork implements PropertyChangedListener
         $classMetadata = $this->_em->getClassMetadata(get_class($entity));
         $idHash = implode(' ', $this->_entityIdentifiers[$oid]);
         if ($idHash === '') {
-            throw DoctrineException::entityMustHaveIdentifyToBeRemovedFromIdentityMap($entity);
+            throw new \InvalidArgumentException("The given entity has no identity.");
         }
         $className = $classMetadata->rootEntityName;
         if (isset($this->_identityMap[$className][$idHash])) {
@@ -1212,8 +1212,8 @@ class UnitOfWork implements PropertyChangedListener
                 $this->scheduleForInsert($entity);
                 break;
             case self::STATE_DETACHED:
-                throw DoctrineException::notImplemented("Behavior of save() for a detached entity "
-                        . "is not yet defined.");
+                throw new \InvalidArgumentException(
+                        "Behavior of save() for a detached entity is not yet defined.");
             case self::STATE_REMOVED:
                 // Entity becomes managed again
                 if ($this->isScheduledForDelete($entity)) {
@@ -1224,7 +1224,7 @@ class UnitOfWork implements PropertyChangedListener
                 }
                 break;
             default:
-                throw DoctrineException::invalidEntityState($entityState);
+                throw ORMException::invalidEntityState($entityState);
         }
         
         $this->_cascadePersist($entity, $visited);
@@ -1277,9 +1277,9 @@ class UnitOfWork implements PropertyChangedListener
                 $this->scheduleForDelete($entity);
                 break;
             case self::STATE_DETACHED:
-                throw DoctrineException::detachedEntityCannotBeRemoved();
+                throw ORMException::detachedEntityCannotBeRemoved();
             default:
-                throw DoctrineException::invalidEntityState($entityState);
+                throw ORMException::invalidEntityState($entityState);
         }
 
         $this->_cascadeRemove($entity, $visited);