SBS 2003 and SQL 2000 unable to connect via internet

Hi,

I have been reading everything I can in the Knowledge base and here about
connection problems and am still unable to resolve my problem

In the connection string I use the IP address for the SQL Server and it
works fine when I'm connected to the LAN. If I disconnect from the LAN and
rely only on an Internet connection I cannot connect, nor can any of our
employees.

Error: SQL Sserver does not exist or access denied.

This is a VB.NET application which will allow some of our employees to work
remotely using the data on our SQL 2000 sp3a on Small Business Server 2003.
On the LAN I can use either the IP address or the DNS name and the
application works perfectly.

Is there something about SBS 2003 that could be preventing access to port
1433 via the internet connection.

Server has dual network cards, one for LAN and one for Broadband.

Any help would be appreciated.

Thank you
--
Terry Bailey