SQLConnection Threw Exception Of Type System.InvalidOperationException

My SqlConnection is causing an error "sqlConn.ServerVersion threw an exception of type System.InvalidOperationException". Everything I have read seems to suggest that there is a problem with my SQLConnection parameters but as you can see from the commeted code below I have tried three different servers with four different configurations.  I am out of ideas on what is causing the error. 

Thanks - Amy

Here is a section of my code:

String sqlStmt = "Select [UserName], [Password], [Last], [First] from Contacts Where Login=@Uid AND Password=@Pwd";

SqlConnection sqlConn = new SqlConnection("Data Source=localhost;Initial Catalog=test;Integrated Security=SSPI;");
//SqlConnection sqlConn = new SqlConnection("Data Source=pe2800;Initial Catalog=test;Integrated Security=SSPI;");
//SqlConnection sqlConn = new SqlConnection("Data Source=HorizonDC02;Initial Catalog=test;Integrated Security=SSPI;");
//SqlConnection sqlConn = new SqlConnection("Data Source=HorizonDC02;Initial Catalog=test;User ID=username;Password=password;");

SqlCommand sqlCmd = new SqlCommand(sqlStmt, sqlConn);
sqlCmd.Parameters.Add("@Uid", SqlDbType.VarChar, 30).Value = uid;
sqlCmd.Parameters.Add("@Pwd", SqlDbType.VarChar, 30).Value = pwd;
sqlCmd.Connection.Open();