Expecting non-empty string for 'providerInvariantName' parameter.

I am trying to run a SQL query using a connection string defined in the web.config (site and workflow web.config files)  however I am getting an error:

Error: Unhandled exception: 'One or more errors occurred.' in activity '1.5: SqlQuery'.

  One or more errors occurred.

 

    Expecting non-empty string for 'providerInvariantName' parameter.

 

External Activity: 153 bytes received by client

<add name="SDE" providerName="System.Data.SqlClient" ConnectionString="Data Source=DB\SQL2008;Initial Catalog=Edit;Integrated Security=False;User ID=test;Password=test" />

Any ideas?  I added  providerName="System.Data.SqlClient" based on what the internet said, but that didn't seem to work.  Does anyone have this working?

-Jake