Attempt to address Mantis #1905, #1909

Prevent re-sequencing of resent packets. Thanks, ckrinke, for
catching that, it is what was happening.

OpenSim/Region/ClientStack/LindenUDP/LLPacketHandler.cs

@@ -240,6 +240,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     return;
             }
 
+			packet.Header.Sequence = 0;
+
             lock (m_NeedAck)
             {
                 DropResend(id);
@@ -724,6 +726,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             packet.TickCount = System.Environment.TickCount;
 
             // Assign sequence number here to prevent out of order packets
+			if(packet.Header.Sequence == 0)
+			{
 				packet.Header.Sequence = NextPacketSequenceNumber();
 
 				lock (m_NeedAck)
@@ -736,6 +740,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 								item.Identifier);
 					}
 				}
+			}
 
             // Actually make the byte array and send it
             try