Fixed mounting problem described in

http://mail.zope.org/pipermail/zodb-dev/2005-December/009662.html
Basic symptom was lots of conflict in sessions.
Unit test included.

lib/python/Products/ZODBMountPoint/MountedObject.py

@@ -142,12 +142,11 @@ class MountedObject(SimpleItem):
         self.id = id
 
     def _getMountedConnection(self, anyjar):
-        db_name = self._getDBName()
-        try:
-            conn = anyjar.get_connection(db_name)
-        except KeyError:
-            conn = self._getDB().open()
-        return conn
+        # This creates the DB if it doesn't exist yet and adds it
+        # to the multidatabase
+        self._getDB()
+        # Return a new or existing connection linked to the multidatabase set
+        return anyjar.get_connection(self._getDBName())
 
     def mount_error_(self):
         return self._v_connect_error

lib/python/Products/ZODBMountPoint/tests/testMountPoint.py

@@ -177,6 +177,21 @@ class MountingTests(unittest.TestCase):
                      'exists': 1}]
         self.assertEqual(expected, status)
 
+    def test_close(self):
+        app = self.app
+        app.mount1.a1 = '1'
+        app.mount2.a2 = '2'
+        app.a3 = '3'
+        conn1 = app.mount1._p_jar
+        conn2 = app.mount2._p_jar
+        transaction.abort()
+        # Close the main connection
+        app._p_jar.close()
+        self.assertEqual(app._p_jar._opened, None)
+        # Check that secondary connections have been closed too
+        self.assertEqual(conn1._opened, None)
+        self.assertEqual(conn2._opened, None)
+
 
 def test_suite():
     return unittest.makeSuite(MountingTests, 'test')