Yes, my idea was correct for tupac: VPN+NAT, connected to all servers except server.war2.ru.
The problem is:
server blocks all the ICMP packets except request and reply. Maybe your routing scheme uses icmp redirect some way? That will be blocked by the server.
That means your nat is not properly configured, so server has to send icmp redirect packets, that helps to fix your routing.
Server.war2.ru doesn't send icmp redirect, i don't plan to allow that packets, so make sure your routes on NAT are proper.
If problem happened after entering login/pass, it could be related with UDP traffic.