I have an application that connects to a named SQL Server 2005 Express instance using 127.0.0.1\INSTNAME. This has always worked. However, if I install SQL Server 2008 (any edition) on the same machine, the application can no longer connect to the SQL Server 2005 instance using 127.0.0.1. I tried connecting using SQL Management Studio and it too could not make a connection using 127.0.0.1. I then tried .\INSTNAME and that worked. Changing the application to use .\INSTNAME is not an option at present.
Does anybody have a workaround for this issue. It doesn't have to be permanent since the application in question is an installer.