If you try to connect from a SSIS 2008 Management Studio to SQL 2005 Integration Services, it will fail. This is currently listed as a by-design scenario, and I will update this information if there is any hope of this changing.
TITLE: Connect to Server
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Cannot connect to my2005server.
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ADDITIONAL INFORMATION:
Failed to retrieve data for this request. (Microsoft.SqlServer.Management.Sdk.Sfc)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&LinkId=20476
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Connect to SSIS Service on machine "my2005server" failed:
Class not registered.
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Connect to SSIS Service on machine "my2005server" failed:
Class not registered.
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BUTTONS:
OK
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Currently this has been brought up to the SQL Server product groups, on these threads for example:
https://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=363922
https://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=363010
http://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=315076
http://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=412929