Trying to replace Cisco 2514 and IPCop with MT 2.9.40

I am Trying to replace Cisco 2514 and IPCop with MT 2.9.40

This is a server hosting service with a 5mb ISP link and a routed public network via a Cisco 2514.
We have a IPCop to firewall our internal network and our web/email server.
I want to use a single MT to provide the same services.
Current configuration..

        --------------
ISP --> | cisco 2514 |  public - 10.100.0.254/29
        --------------  Default route 10.100.0.248
             |
        -----------      Routed Public Network
        | Switch  | ->   10 web servers
        -----------      10.90.0.126/26
             |
             | Public address 10.90.0.100
        -----------    
        | IPCop   | Public address 10.90.0.100
        |         | Private NATed Network 192.168.12.254/24
        | DSTnat  | ->   1 Private web server
        | SRCnat  | ->   5 Private Desktops
        -----------    

I am trying to change to a single MT 2.9.40 with 3 interfaces and 2 switches and MT providing the SRCnat and DSTnat.

        --------------
ISP --> | MT 2.9.40  |  public - 10.100.0.254/29
eth1    --------------  Default route 10.100.0.248
           |    eth2 |
           |    -----------      Routed Public Network
           |    | Switch  | ->   10 web servers
           |    -----------      10.90.0.126/26
           | eth3
        -----------    
        | Switch  | Private NATed Network 192.168.12.254/24
        |         | Public address 10.90.0.100
        |         | ->   1 Private web server
        |         | ->   5 Private Desktops
        -----------    

I can't get dst-nat to work from the public to private networks.
The src-nat works well and with the correct src address.
Please help me.

Configuration is 3 interfaces.
eth1 - public - 10.100.0.254/29 
   to ISP default route 10.100.0.248
eth2 - routed network from ISP - 10.90.0.126/26
   This is where all the servers are connected.
   A second address in the interface 10.90.0.100
     for the private net nat.
eth3 - privated nat network - 192.168.12.254/24
    The private machines are here and 1 private server
-----
/ ip firewall nat 
add chain=srcnat src-address=192.168.12.0/24 action=src-nat \
    to-addresses=10.90.0.100 to-ports=0-65535 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=25 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=25 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=3389 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=3389 comment="" \
    disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=500 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=500 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=4125 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=4125 comment="" \
    disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=1701 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=1701 comment="" \
    disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=80 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=80 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=444 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=444 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=443 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=443 comment="" disabled=no 
add chain=dstnat dst-address=10.90.0.100 protocol=tcp dst-port=1723 \
    action=dst-nat to-addresses=192.168.12.1 to-ports=1723 comment="" \
    disabled=no 
------
thanks
DEH