Invalid connection error on SQL Server 2008 I have this third party application that is interfacing with a MS SQL Server and I have some issue migrating its database from a MS SQL Server 2005 to A MS SQL Server 2008. The application was provided by a manufacturing company (it interfaces with a machinery) but produced by someone else (let's say a third third-part). I tried to contact our provider (the machinery producer), but basically they said they cannot reach the application developer and the product is unsupported. So I am on my own to solve this thing.

Currently the database instance is located on a box with the following features:
-Virtualized Windows 2003 SBS Server
-SQL Server 2005 (9.4.5000.00)

It has to be migrated to the following:
-Virtualized Windows 2008 R2
-SQL Server 2008 R2 SP2 (10.52.4000.0)

Both SQL Server are listening on the standard 1433 port.
The application connects to the DB through SQL authentication on a local network.

I have successfully installed the server and the db (.mdf and .ldf files) on the new MS SQL 2008 server: I can query the db through Sql Server Management Studio and it returns correct results. The DB is really simple: few tables with few relationships: basically the application just needs to send a code and retrieve a string. I can also connect to the db through the SQL Server Management Studio (using both windows and SQL authentication), but the application fails to connect, issuing this error: "[DBNETLIB][ConnectionOpen (Invalid Instance()).] Invalid connection".

I am not a MS SQL Server expert (I use it just for this application), can someone help me out?
Thanks,
Gio
I found a similar question with an answer, this one https://superuser.com/questions/314206/cannot-connect-to-sql-server-from-excel-2007 on superuser. It turned out that for some reason, on the MS SQL Server 2008 I had to put a named instance and not just the name of the server, e.g. if the server name is "yoda", on the application configuration I have just to put "yoda" if the backend is a MS SQL Server 2005, if I use MS SQL Server 2008 I have to put "yoda\sqlexpress,1433". I do not know if an alternative solution could be updating some libraries.