Why is Snapshot failing to create any backups?

I just completed installing and configuring Snapshot, so I tried to run an initial test run Backup. I setup a weekly full site backup and then told it to run immediately. The backup hung on 'Creating Archive' for over an hour until I had to close the page and it only created a 39 byte file. This pattern repeated 3 times. 3 attempts. Still no backups. Any suggestions?

Hosting is Shared Dreamhost.
I am running WP Multisite.