If I use the trusted connection, this kit works fine. However, if I go to the web.config file to comment this line out and user the authentication connection (i.e. user name and password), it always complain and cannot connect to the database.

I am creating a web site by using this kit and trying to put it on a cumercial host server. The vendor's database is on a different server (not on the web app host server). So, I have to use the authentication connection.

I am wondering if any one had the same problem and how did you solve it.

Hope some one can help me out.

Thanks. 

The host must setup the database server to accept sql authentication for username and password to work. And set you up as a user.
I run several instances of sql server 2000 this way. 
On the starter kit it might look like this.
<add key="ConnectionString" value="server=BlaBla\Storesql;database=Commerce;uid=CommerceUser;pwd=CommerceUser;" />
    </appSettings>

Hope this helps.

Art Bacon