Error connecting to named instance

I had to install a new instance of SQL Server 2008 R2 Express on Windows 2007 because our SQL Server 2008 R2 Trial version ended (It's just a development machine). I was able to connect to the Express version using SSMS using the machine name\instance name but couldn't connect using the web config from our web service (error establishing connection to SQL Server - error 40). Everything is local. I did read that you if you have a named instance, it connects with dynamic ports but I wasn't sure if this was true when everything is local but I did try changing the port to a fixed one (added it to the connection string) and opened the windows firewall but it still didn't work. So I then changed the port to the default port of 1433 and it did work. So three questions: 1) does that mean I didn't open the firewall correctly when I had another port (I used 1435, which didn't seem to be in use by other program)? 2) In using 1433, it complained that the database name was incorrect and ...