I have a configuration (2 bm38 vpn servers) where the slave server is
behind a dsl router (DMZ).
I have these error messages:

Master server ike console: Retransmit timer expired :Peer lost our reply
retransmit the old packet to xxx.xxx.xxx.xxx

Slave server ike console: Processed ID-PAYLOAD unsuccesful - Received main
mode message in a wrong state.

(I tried to connect the slave server to the master's public network, I
changed the ip addresses (vpn configs too), and it worked. So I think it's
not a config problem.)