You are trying to open a DTS package (yes some people still use DTS packages) and receive the following error:

Error opening a DTS package 
TITLE: Open DTS 2000 Package 
------------------------------ 
  
here were errors loading package "MyDTSPackageName": 
  
[DBNETLIB][ConnectionOpen (Invalid Instance()).]Invalid connection. (Microsoft.SqlServer.DtsObjectExplorerUI)

First let me point out that the “here were errors” is correct. The typo makes it MUCH easier to find this particular error. I have to admit I don’t know the mechanics of why this particular error shows up. What I can tell you is that I see it any time we have DNS Aliasing set up on an instance and the user is connecting to the instance using the alias.

For example there is an instance on a server called “NewServerName” and you want your users to continue to connect to the instance using the old server name “OldServerName”. You create a DNS alias that points the IP address for the server to an additional name (say “OldServerName”). You can now connect to the instance with either “NewServerName” or “OldServerName”. Unfortunately when connecting using “OldServerName” you can’t open DTS packages.

So what’s the solution? The easiest one (and the only one I’ve found so far) is to connect using “NewServerName”. If you want you can go ahead and set up a cliconfg alias pointing “OldServerName” to “NewServerName”. This way you completely avoid the DNS alias and as far everything is concerned you are connecting using the “real” name (“NewServerName”).

If you are still dealing with DTS packages you might find these posts helpful.

Finding active DTS packages
Script to find DTS Connections (No not SSIS)