Here is your problem - I have received this before on a computer with a new SQL installation.

From the Microsoft knowledge database at: http://support.microsoft.com/kb/555332

CAUSE

The SQL server has been configured to operate in "Windows Authentication Mode (Windows Authentication)" and doesn't allow
the use of SQL accounts.

RESOLUTION

Change the Authentication Mode of the SQL server from "Windows Authentication Mode (Windows Authentication)"
to "Mixed Mode (Windows Authentication and SQL Server Authentication)".

You do this by right-clicking your local "Servername\SQLInstancename" in Management Studio, selecting properties, choose "Security" in the menu on the left and choosing the radio button next to "SQl Server and Windows Authenticafion mode".

Good luck,

Mike

Is that your real connection string? Even if your database is actually named DotNetNuke and userid at myuserid and pwd: mypassword still the server needs to have the server name followed by a slash"\" and SQL Instance name ("mysqlserver\mysqlinstancename")  for a localhost machine or  mysqlserver.com for the actuall online database server name.

If that is not your real connection string then you need to provide one. The error message is a standard one for a lot of connection problems so since you say you have the SQL Server set up in mixed mode authentication it must be another connection problem.

Good luck,

Mike