Maybe the problem is related to this?
Multiple Road Warrior L2TP/IPsec clients behind NAT
http://forum.mikrotik.com/t/multiple-road-warrior-l2tp-ipsec-clients-behind-nat-solved/118206/1
Maybe the problem is related to this?
Multiple Road Warrior L2TP/IPsec clients behind NAT
http://forum.mikrotik.com/t/multiple-road-warrior-l2tp-ipsec-clients-behind-nat-solved/118206/1