Connecting Firebox to DSL Modem problems

I'm in a bind.  I need to get this modem up and running on my firebox core x750e, but it is giving me problems.  

I have a speedstream 4200 modem.  The DSL line is set up with a static IP and I can connect the modem directly to a laptop that is configured with the proper IP addresses and the Internet works great.  When I plug that modem directly to the firebox and set the IP addresses in the network config section of the policy manager, the system manager shows the external DSL connection as [failed].  I also cannot ping the IP of the connection externally, so that confirms to me that the system manager is correct.  

I'm not sure what my next step should be.  I thought of buying a router and setting up NAT between it and the firebox, because I can successfully connect through a router with the static IP information I was given..  but that doesn't seems a little ridiculous.  I also need to have this DSL modem as the gateway for one of the branch office VPNs, so I don't know how that would work with the router in between.  

Thanks for your help guys.  I need to get this fixed today because im flying out to the remote office tomorrow morning!