"SQL Server does not exist or access denied" error

I'm trying to create to set up connection between my web application on the server and
the database on another box and getting "SQL Server does not exist or access denied" error.
Both the web server and the database machine are Windows 2003 Server, there's no firewall
enabled, there's mixed authentication enabled on the sql server. The machines are not on the
same domain so I'm using SQL Server authentication from web.config. Here's my connection string:
<add key="ConnectionString" value="Server=sqlboxip;User id=sqlaccountname;Pwd=sqlpass;Initial catalog=dbname">
I've also got <identity impersonate="true"> set in web.config.
Had it the connection working at some stage but then with more tweaking and app reinstall
back square one... Please help!</identity></add>Hi,
Are you able to connect to the SQL Server Database using the same credentials from SQL Server (Enterprise Manager or Query Analyzer?)
Thanks.|||Yes, I can connect to it from my dev box in ASP.NET
|||Did you set the connection string of your connection on that page of the app?

I put this in the page load.
this.cnMainConnection.ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionsString"].ToString();

|||Hi,
Ok, can you post the code which you are trying to execute.
Thanks.