Rackspace backup timeout

I'm unable to get Rackspace backups working. Username, API key, and server location filled in, however on running either a scheduled or manual backup I see "Download timed out" error message. I see this both in virtualmin and via command line using sudo virtualmin list-rs-containers. If I change the username to make it incorrect I see "Authentication at https://lon.auth.api.rackspacecloud.com/v1.0 failed : Invalid HTTP response : HTTP/1.1 401 Unauthorized" so there appears to be some sort of connection made. Has anyone any ideas why it's not working?