Thank you kindly, Patnad, for a patch that:

This is to handle the changes in the v1.23 viewer 
of LL regarding the adult rating. With this patch 
a region can be changed to the adult rating from 
LL viewer v1.23 and above.

OpenSim/Framework/RegionInfo.cs

@@ -334,6 +334,11 @@ namespace OpenSim.Framework
             get { return m_objectCapacity; }
         }
 
+        public byte AccessLevel
+        {
+            get { return (byte)Util.ConvertMaturityToAccessLevel((uint)m_regionSettings.Maturity); }
+        }
+
         public void SetEndPoint(string ipaddr, int port)
         {
             IPAddress tmpIP = IPAddress.Parse(ipaddr);
@@ -691,5 +696,6 @@ namespace OpenSim.Framework
             regionInfo.ServerURI = serverURI;
             return regionInfo;
         }
+
     }
 }

OpenSim/Framework/Util.cs

@@ -1045,5 +1045,29 @@ namespace OpenSim.Framework
 
             return guid;
         }
+
+        public static byte ConvertMaturityToAccessLevel(uint maturity)
+        {
+            byte retVal = 0;
+            switch (maturity)
+            {
+                case 0: //PG
+                    retVal = 13;
+                    break;
+                case 1: //Mature
+                    retVal = 21;
+                    break;
+                case 2: // Adult
+                    retVal = 42;
+                    break;
+            }
+
+            return retVal;
+
+        }
+
+
+
+
     }
 }