Snapshot 18.104.22.168 installed without issue, and I configured and enabled both the local and dropbox destinations. Then I started creating test snapshots, always running them manually right away. When I click "create snapshot" I expect to see a progress screen, but it takes me back to the snapshot list, and I see that the snapshot that I created is there, but without any archives. If I schedule the snapshot, I do get archives provided there is site activity. If I edit the snapshot, and choose "Save settings and run backup now" it again just returns to the All Snapshots screen, and no archive is added.
I would like to have a scheduled backup daily or hourly, but have the ability to initiate a backup just before a major change is taken. This does seem to allow for that, but is not working.
I am running CentOS 6 with SELinux enabled (and configured for Apache) running WP 3.4.2, and all other site functions and WPMU plugins are working as they should.