I had a similar problem when I opened the sv2i file initially. If you look under the backup date drop down box are you able to select the timestamp of your E: backup? Once I did this it loaded the storage group without any issues. Our backup includes c: and e: so the sv2i attempts to load the c: backup which does not have the Exchange data or the backup information folder (both on e:). Hope this helps!
David, I am also having this issue, and none of the solutions have helped.
Can you suggest anything else? I know that the exchange install and databases are on different volumes on my exchange server, but the backup is doing both drives. I also make sure to open both drives int eh granular restore before hitting the exchange mail tab, but I still get the error.
If you have access to a different machine, you can try installing GRO somewhere else. There is a document related to this issue when using BESR GRO 8.5.
This document suggests two possible work arounds if there are no other machines which can house GRO.