In the CTP releases before June, you may have run into an issue with connecting to MSDB when attempting to enumerate packages there. You probably received an error message something like this:
The ExistsOnSQLServer method has encountered OLE DB error code 0x80004005 ([DBNETLIB][ConnectionOpen (SECDoClientHandshake()).]SSL Security error.). The SQL statement issued has failed.
IS will only communicate with the server through an encrypted connection to protect sensitive data in packages. What this error is telling you is essentially that IS is unable to get an encrypted connection to the server. Yukon provides encrypted connections using the "Encrypt Connection" setting. To find out more about this, take a look at books online here: ms-help://MS.SQLCC.v9/MS.SQLSVR.v9.en/udb9/html/e1e55519-97ec-4404-81ef-881da3b42006.htm
This is new in SQL 2K5. Because of the security policy with SSIS, and because SQL 2K does not support this feature, SSIS is unable to use SQL 2K as a storage location for packages and never will.
If you're seeing this problem in SQL 2K5 Pre-June CTPs, it's because you don't have a trusted certificate provisioned for your server. The above link talks about how to remedy that. If you don't have a trusted certificate, in the June CTP, the server will automatically provision a self-signed certificate and enable the encrypted connection. This is only available in the June CTP, however.
Resources:
ms-help://MS.SQLCC.v9/MS.SQLSVR.v9.en/udb9/html/e1e55519-97ec-4404-81ef-881da3b42006.htm
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q276553
http://support.microsoft.com/kb/318605
Universe.Earth.Software.Microsoft.SQLServer.IS.KirkHaselden