Hi Alex,
Yep, that's the problem. My Exchange 2003 setup is a cluster also. The test system I tried it on is also a cluster. I don't have any non-clustered Exchange servers but I assume it would work on them.
My SQL instances remain working, but they are not running on a cluster.
Incidentally, even though my Exchange store is selected in a saved user selection list, the backup still does not work. Everything else works, but it fails to connect to the store and misses that part of the backup.
As you stated, creating a new selection list doesn't even give the Exchange options at all.
I'm feeling better knowing that it isn't just me! :)
Cheers,
David