.net sqllite throwing exception

I am doing the simple task of opening a connection to my .sdf database. I have done this before in previous projects, but this time my program freezes. I placed a break point where the program gets stuck. conn.open(); shows this:

'conn.ServerVersion' threw an exception of type 'System.InvalidOperationException'

Here is my code:

private int nextID(string table, string columnName) {

// 1. Create your SQL Connection
// 2. Create and open a connection object
int returnvalue;
using (SqlConnection conn = new SqlConnection(Properties.Settings.Default.territories2ConnectionString))
{

// 3. Open the Connection
conn.Open(); //<--program will not got past this point. It freezes!

// 4. Create the SQL Command and assign it it a string
string strSQLCommand = "SELECT MAX(" + columnName + ") FROM " + table;

// 5. Execute the SQL Command
SqlCommand command = new SqlCommand(strSQLCommand, conn);

// 6. Use ExecuteScalar() to return the first result
returnvalue = (int)command.ExecuteScalar();

// 7. Close the Connection
conn.Close();
}

// 8. Return the Value plus 1
returnvalue++;
return returnvalue;

}

I have spent 2 days searching the internet, and have found nothing. I even refered to my past projects, and still nothing.

Any suggestions?