Answer to a very old problem..I know.

But I got into this situation when we changed our server.

The maintenance plans are SSIS packages stored in the Package Store of your server.

Once you upgrade your server and export your packages, the XML for the package wont get changed automatically and SSMS doesnt have any way of making that change for you.

Hence you will need to change the XML itself. Please use the script found at

http://msdn.microsoft.com/en-us/library/ms143799(v=sql.90).aspx (Scroll to the comments section..some good fella provided the script in there).

This script works perfectly fine and you will be able to see the changes being made. Good Luck to anyone facing the same issue.