Connection to SQL Server 2005 over a VPN

I have configured a VPN connection between two offices. I have TCP/IP connectivity between both the server and client machine, and I have the firewalls open to the specific ports I need. I can connect to my SQL server using MS Management Studio with no problems,from the client machine. When I try to connect using the Directors Assistant software I get an error 26, cannot connect to the server, from the client machine. There is a registry entry with the Database String and I have tried several different methods as mentioned on this forum. Examples are as follows:
Connection String=192.168.1.10,49160; Initial Database=DirectorsAssistant; User Id=##; Password=##. Can anyone help me hear? I can provide more info if needed but this has stumped me. I really appreciate any help.