double nat routing

[giagni]

hi all

I'have got a networking issue that make me crazy...

+--------+
|--web --|
+--------+
    |
    |
88.99.100.0/26  (em1)
+--------+
|-gate1--|
+--------+
10.0.1.1  (em0)
    |
    |                    +---------+
    +---------10.0.1.5---|webserver|
    |                    +---------+
    |
10.0.1.20  (bce0)
+--------+
|-gate2--|
+--------+
192.168.4.1  (bce1)
    |
    |
192.168.4.2
+--------+
|client1-|
+--------+

In a network like that, where

gate1 nat on interface em1
gate2 nat on interface bce0
both are freebsd gateway machine with ipfw+natd


So... client1 can access on internet,
but cant access on my internal webserver

Is not a problem of ipfw rules. I'm sure.
I suppose the route to internal webserver can establish but cant'return to client1

any suggestions?
Thanks